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2024-10-20x86/kvm: Override default caching mode for SEV-SNP and TDXKirill A. Shutemov
AMD SEV-SNP and Intel TDX have limited access to MTRR: either it is not advertised in CPUID or it cannot be programmed (on TDX, due to #VE on CR0.CD clear). This results in guests using uncached mappings where it shouldn't and pmd/pud_set_huge() failures due to non-uniform memory type reported by mtrr_type_lookup(). Override MTRR state, making it WB by default as the kernel does for Hyper-V guests. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Suggested-by: Binbin Wu <binbin.wu@intel.com> Cc: Juergen Gross <jgross@suse.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Reviewed-by: Juergen Gross <jgross@suse.com> Message-ID: <20241015095818.357915-1-kirill.shutemov@linux.intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-10-20KVM: Remove unused kvm_vcpu_gfn_to_pfn_atomicDr. David Alan Gilbert
The last use of kvm_vcpu_gfn_to_pfn_atomic was removed by commit 1bbc60d0c7e5 ("KVM: x86/mmu: Remove MMU auditing") Remove it. Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org> Message-ID: <20241001141354.18009-3-linux@treblig.org> [Adjust Documentation/virt/kvm/locking.rst. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-10-20KVM: Remove unused kvm_vcpu_gfn_to_pfnDr. David Alan Gilbert
The last use of kvm_vcpu_gfn_to_pfn was removed by commit b1624f99aa8f ("KVM: Remove kvm_vcpu_gfn_to_page() and kvm_vcpu_gpa_to_page()") Remove it. Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org> Message-ID: <20241001141354.18009-2-linux@treblig.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2024-10-19io_uring: IORING_OP_F[GS]ETXATTR is fine with REQ_F_FIXED_FILEJens Axboe
Rejection of IOSQE_FIXED_FILE combined with IORING_OP_[GS]ETXATTR is fine - these do not take a file descriptor, so such combination makes no sense. The checks are misplaced, though - as it is, they triggers on IORING_OP_F[GS]ETXATTR as well, and those do take a file reference, no matter the origin. Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-19getname_maybe_null() - the third variant of pathname copy-inAl Viro
Semantics used by statx(2) (and later *xattrat(2)): without AT_EMPTY_PATH it's standard getname() (i.e. ERR_PTR(-ENOENT) on empty string, ERR_PTR(-EFAULT) on NULL), with AT_EMPTY_PATH both empty string and NULL are accepted. Calling conventions: getname_maybe_null(user_pointer, flags) returns * pointer to struct filename when non-empty string had been successfully read * ERR_PTR(...) on error * NULL if an empty string or NULL pointer had been given with AT_EMPTY_PATH in the flags argument. It tries to avoid allocation in the last case; it's not always able to do so, in which case the temporary struct filename instance is freed and NULL returned anyway. Fast path is inlined. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-19teach filename_lookup() to treat NULL filename as ""Al Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-19Merge tag 'io_uring-6.12-20241019' of git://git.kernel.dk/linuxLinus Torvalds
Pull one more io_uring fix from Jens Axboe: "Fix for a regression introduced in 6.12-rc2, where a condition check was negated and hence -EAGAIN would bubble back up up to userspace rather than trigger a retry condition" * tag 'io_uring-6.12-20241019' of git://git.kernel.dk/linux: io_uring/rw: fix wrong NOWAIT check in io_rw_init_file()
2024-10-19block: Add bdev atomic write limits helpersJohn Garry
Add helpers to get atomic write limits for a bdev, so that we don't access request_queue helpers outside the block layer. We check if the bdev can actually atomic write in these helpers, so we can avoid users missing using this check. Suggested-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: John Garry <john.g.garry@oracle.com> Link: https://lore.kernel.org/r/20241019125113.369994-4-john.g.garry@oracle.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-19fs/block: Check for IOCB_DIRECT in generic_atomic_write_valid()John Garry
Currently FMODE_CAN_ATOMIC_WRITE is set if the bdev can atomic write and the file is open for direct IO. This does not work if the file is not opened for direct IO, yet fcntl(O_DIRECT) is used on the fd later. Change to check for direct IO on a per-IO basis in generic_atomic_write_valid(). Since we want to report -EOPNOTSUPP for non-direct IO for an atomic write, change to return an error code. Relocate the block fops atomic write checks to the common write path, as to catch non-direct IO. Fixes: c34fc6f26ab8 ("fs: Initial atomic write support") Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: John Garry <john.g.garry@oracle.com> Link: https://lore.kernel.org/r/20241019125113.369994-3-john.g.garry@oracle.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-19block/fs: Pass an iocb to generic_atomic_write_valid()John Garry
Darrick and Hannes both thought it better that generic_atomic_write_valid() should be passed a struct iocb, and not just the member of that struct which is referenced; see [0] and [1]. I think that makes a more generic and clean API, so make that change. [0] https://lore.kernel.org/linux-block/680ce641-729b-4150-b875-531a98657682@suse.de/ [1] https://lore.kernel.org/linux-xfs/20240620212401.GA3058325@frogsfrogsfrogs/ Fixes: c34fc6f26ab8 ("fs: Initial atomic write support") Suggested-by: Darrick J. Wong <djwong@kernel.org> Suggested-by: Hannes Reinecke <hare@suse.de> Reviewed-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: John Garry <john.g.garry@oracle.com> Link: https://lore.kernel.org/r/20241019125113.369994-2-john.g.garry@oracle.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-19octeon_ep: Add SKB allocation failures handling in __octep_oq_process_rx()Aleksandr Mishin
build_skb() returns NULL in case of a memory allocation failure so handle it inside __octep_oq_process_rx() to avoid NULL pointer dereference. __octep_oq_process_rx() is called during NAPI polling by the driver. If skb allocation fails, keep on pulling packets out of the Rx DMA queue: we shouldn't break the polling immediately and thus falsely indicate to the octep_napi_poll() that the Rx pressure is going down. As there is no associated skb in this case, don't process the packets and don't push them up the network stack - they are skipped. Helper function is implemented to unmmap/flush all the fragment buffers used by the dropped packet. 'alloc_failures' counter is incremented to mark the skb allocation error in driver statistics. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: 37d79d059606 ("octeon_ep: add Tx/Rx processing and interrupt support") Suggested-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19octeon_ep: Implement helper for iterating packets in Rx queueAleksandr Mishin
The common code with some packet and index manipulations is extracted and moved to newly implemented helper to make the code more readable and avoid duplication. This is a preparation for skb allocation failure handling. Found by Linux Verification Center (linuxtesting.org) with SVACE. Suggested-by: Simon Horman <horms@kernel.org> Suggested-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19bnxt_en: replace ptp_lock with irqsave variantVadim Fedorenko
In netpoll configuration the completion processing can happen in hard irq context which will break with spin_lock_bh() for fullfilling RX timestamp in case of all packets timestamping. Replace it with spin_lock_irqsave() variant. Fixes: 7f5515d19cd7 ("bnxt_en: Get the RX packet timestamp") Reviewed-by: Michael Chan <michael.chan@broadcom.com> Signed-off-by: Vadim Fedorenko <vadfed@meta.com> Message-ID: <20241016195234.2622004-1-vadfed@meta.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19net: phy: dp83822: Fix reset pin definitionsMichel Alex
This change fixes a rare issue where the PHY fails to detect a link due to incorrect reset behavior. The SW_RESET definition was incorrectly assigned to bit 14, which is the Digital Restart bit according to the datasheet. This commit corrects SW_RESET to bit 15 and assigns DIG_RESTART to bit 14 as per the datasheet specifications. The SW_RESET define is only used in the phy_reset function, which fully re-initializes the PHY after the reset is performed. The change in the bit definitions should not have any negative impact on the functionality of the PHY. v2: - added Fixes tag - improved commit message Cc: stable@vger.kernel.org Fixes: 5dc39fd5ef35 ("net: phy: DP83822: Add ability to advertise Fiber connection") Signed-off-by: Alex Michel <alex.michel@wiedemann-group.com> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Message-ID: <AS1P250MB0608A798661549BF83C4B43EA9462@AS1P250MB0608.EURP250.PROD.OUTLOOK.COM> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19MAINTAINERS: add Simon as an official reviewerJakub Kicinski
Simon has been diligently and consistently reviewing networking changes for at least as long as our development statistics go back. Often if not usually topping the list of reviewers. Make his role official. Acked-by: Eric Dumazet <edumazet@google.com> Acked-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org> Reviewed-by: Simon Horman <horms@kernel.org> Message-ID: <20241015153005.2854018-1-kuba@kernel.org> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19net: plip: fix break; causing plip to never transmitJakub Boehm
Since commit 71ae2cb30531 ("net: plip: Fix fall-through warnings for Clang") plip was not able to send any packets, this patch replaces one unintended break; with fallthrough; which was originally missed by commit 9525d69a3667 ("net: plip: mark expected switch fall-throughs"). I have verified with a real hardware PLIP connection that everything works once again after applying this patch. Fixes: 71ae2cb30531 ("net: plip: Fix fall-through warnings for Clang") Signed-off-by: Jakub Boehm <boehm.jakub@gmail.com> Reviewed-by: Simon Horman <horms@kernel.org> Message-ID: <20241015-net-plip-tx-fix-v1-1-32d8be1c7e0b@gmail.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19be2net: fix potential memory leak in be_xmit()Wang Hai
The be_xmit() returns NETDEV_TX_OK without freeing skb in case of be_xmit_enqueue() fails, add dev_kfree_skb_any() to fix it. Fixes: 760c295e0e8d ("be2net: Support for OS2BMC.") Signed-off-by: Wang Hai <wanghai38@huawei.com> Reviewed-by: Simon Horman <horms@kernel.org> Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com> Message-ID: <20241015144802.12150-1-wanghai38@huawei.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19net/sun3_82586: fix potential memory leak in sun3_82586_send_packet()Wang Hai
The sun3_82586_send_packet() returns NETDEV_TX_OK without freeing skb in case of skb->len being too long, add dev_kfree_skb() to fix it. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Wang Hai <wanghai38@huawei.com> Reviewed-by: Simon Horman <horms@kernel.org> Message-ID: <20241015144148.7918-1-wanghai38@huawei.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19net: pse-pd: Fix out of bound for loopKory Maincent
Adjust the loop limit to prevent out-of-bounds access when iterating over PI structures. The loop should not reach the index pcdev->nr_lines since we allocate exactly pcdev->nr_lines number of PI structures. This fix ensures proper bounds are maintained during iterations. Fixes: 9be9567a7c59 ("net: pse-pd: Add support for PSE PIs") Signed-off-by: Kory Maincent <kory.maincent@bootlin.com> Reviewed-by: Simon Horman <horms@kernel.org> Acked-by: Oleksij Rempel <o.rempel@pengutronix.de> Message-ID: <20241015130255.125508-1-kory.maincent@bootlin.com> Signed-off-by: Andrew Lunn <andrew@lunn.ch>
2024-10-19Merge tag 'scsi-fixes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi Pull SCSI fixes from James Bottomley: "Fixes all in drivers. The largest is the mpi3mr which corrects a phy count limit that should only apply to the controller but was being incorrectly applied to expander phys" * tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: scsi: target: core: Fix null-ptr-deref in target_alloc_device() scsi: mpi3mr: Validate SAS port assignments scsi: ufs: core: Set SDEV_OFFLINE when UFS is shut down scsi: ufs: core: Requeue aborted request scsi: ufs: core: Fix the issue of ICU failure
2024-10-19Merge tag 'ftrace-v6.12-rc3' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull ftrace fixes from Steven Rostedt: "A couple of fixes to function graph infrastructure: - Fix allocation of idle shadow stack allocation during hotplug If function graph tracing is started when a CPU is offline, if it were come online during the trace then the idle task that represents the CPU will not get a shadow stack allocated for it. This means all function graph hooks that happen while that idle task is running (including in interrupt mode) will have all its events dropped. Switch over to the CPU hotplug mechanism that will have any newly brought on line CPU get a callback that can allocate the shadow stack for its idle task. - Fix allocation size of the ret_stack_list array When function graph tracing converted over to allowing more than one user at a time, it had to convert its shadow stack from an array of ret_stack structures to an array of unsigned longs. The shadow stacks are allocated in batches of 32 at a time and assigned to every running task. The batch is held by the ret_stack_list array. But when the conversion happened, instead of allocating an array of 32 pointers, it was allocated as a ret_stack itself (PAGE_SIZE). This ret_stack_list gets passed to a function that iterates over what it believes is its size defined by the FTRACE_RETSTACK_ALLOC_SIZE macro (which is 32). Luckily (PAGE_SIZE) is greater than 32 * sizeof(long), otherwise this would have been an array overflow. This still should be fixed and the ret_stack_list should be allocated to the size it is expected to be as someday it may end up being bigger than SHADOW_STACK_SIZE" * tag 'ftrace-v6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: fgraph: Allocate ret_stack_list with proper size fgraph: Use CPU hotplug mechanism to initialize idle shadow stacks
2024-10-19Merge tag 'ipe-pr-20241018' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/wufan/ipe Pull ipe fixes from Fan Wu: "This addresses several issues identified by Luca when attempting to enable IPE on Debian and systemd: - address issues with IPE policy update errors and policy update version check, improving the clarity of error messages for better understanding by userspace programs. - enable IPE policies to be signed by secondary and platform keyrings, facilitating broader use across general Linux distributions like Debian. - updates the IPE entry in the MAINTAINERS file to reflect the new tree URL and my updated email from kernel.org" * tag 'ipe-pr-20241018' of git://git.kernel.org/pub/scm/linux/kernel/git/wufan/ipe: MAINTAINERS: update IPE tree url and Fan Wu's email ipe: fallback to platform keyring also if key in trusted keyring is rejected ipe: allow secondary and platform keyrings to install/update policies ipe: also reject policy updates with the same version ipe: return -ESTALE instead of -EINVAL on update when new policy has a lower version
2024-10-19Merge tag 'input-for-v6.12-rc3' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input Pull input fixes from Dmitry Torokhov: - a fix for Zinitix driver to not fail probing if the property enabling touch keys functionality is not defined. Support for touch keys was added in 6.12 merge window so this issue does not affect users of released kernels - a couple new vendor/device IDs in xpad driver to enable support for more hardware * tag 'input-for-v6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input: Input: zinitix - don't fail if linux,keycodes prop is absent Input: xpad - add support for MSI Claw A1M Input: xpad - add support for 8BitDo Ultimate 2C Wireless Controller
2024-10-19Merge tag '9p-for-6.12-rc4' of https://github.com/martinetd/linuxLinus Torvalds
Pull 9p fixes from Dominique Martinet: "Mashed-up update that I sat on too long: - fix for multiple slabs created with the same name - enable multipage folios - theorical fix to also look for opened fids by inode if none was found by dentry" [ Enabling multi-page folios should have been done during the merge window, but it's a one-liner, and the actual meat of the enablement is in netfs and already in use for other filesystems... - Linus ] * tag '9p-for-6.12-rc4' of https://github.com/martinetd/linux: 9p: Avoid creating multiple slab caches with the same name 9p: Enable multipage folios 9p: v9fs_fid_find: also lookup by inode if not found dentry
2024-10-19Merge tag 'rust-fixes-6.12-2' of https://github.com/Rust-for-Linux/linuxLinus Torvalds
Pull rust fixes from Miguel Ojeda: "Toolchain and infrastructure: - Fix several issues with the 'rustc-option' macro. It includes a refactor from Masahiro of three '{cc,rust}-*' macros, which is not a fix but avoids repeating the same commands (which would be several lines in the case of 'rustc-option'). - Fix conditions for 'CONFIG_HAVE_CFI_ICALL_NORMALIZE_INTEGERS'. It includes the addition of 'CONFIG_RUSTC_LLVM_VERSION', which is not a fix but is needed for the actual fix. And a trivial grammar fix" * tag 'rust-fixes-6.12-2' of https://github.com/Rust-for-Linux/linux: cfi: fix conditions for HAVE_CFI_ICALL_NORMALIZE_INTEGERS kbuild: rust: add `CONFIG_RUSTC_LLVM_VERSION` kbuild: fix issues with rustc-option kbuild: refactor cc-option-yn, cc-disable-warning, rust-option-yn macros lib/Kconfig.debug: fix grammar in RUST_BUILD_ASSERT_ALLOW
2024-10-19io_uring/rw: fix wrong NOWAIT check in io_rw_init_file()Jens Axboe
A previous commit improved how !FMODE_NOWAIT is dealt with, but inadvertently negated a check whilst doing so. This caused -EAGAIN to be returned from reading files with O_NONBLOCK set. Fix up the check for REQ_F_SUPPORT_NOWAIT. Reported-by: Julian Orth <ju.orth@gmail.com> Link: https://github.com/axboe/liburing/issues/1270 Fixes: f7c913438533 ("io_uring/rw: allow pollable non-blocking attempts for !FMODE_NOWAIT") Signed-off-by: Jens Axboe <axboe@kernel.dk>
2024-10-19iio: gts-helper: Fix memory leaks for the error path of ↵Jinjie Ruan
iio_gts_build_avail_scale_table() If per_time_scales[i] or per_time_gains[i] kcalloc fails in the for loop of iio_gts_build_avail_scale_table(), the err_free_out will fail to call kfree() each time when i is reduced to 0, so all the per_time_scales[0] and per_time_gains[0] will not be freed, which will cause memory leaks. Fix it by checking if i >= 0. Cc: stable@vger.kernel.org Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers") Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> Link: https://patch.msgid.link/20241016012453.2013302-1-ruanjinjie@huawei.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
2024-10-19iio: gts-helper: Fix memory leaks in iio_gts_build_avail_scale_table()Jinjie Ruan
modprobe iio-test-gts and rmmod it, then the following memory leak occurs: unreferenced object 0xffffff80c810be00 (size 64): comm "kunit_try_catch", pid 1654, jiffies 4294913981 hex dump (first 32 bytes): 02 00 00 00 08 00 00 00 20 00 00 00 40 00 00 00 ........ ...@... 80 00 00 00 00 02 00 00 00 04 00 00 00 08 00 00 ................ backtrace (crc a63d875e): [<0000000028c1b3c2>] kmemleak_alloc+0x34/0x40 [<000000001d6ecc87>] __kmalloc_noprof+0x2bc/0x3c0 [<00000000393795c1>] devm_iio_init_iio_gts+0x4b4/0x16f4 [<0000000071bb4b09>] 0xffffffdf052a62e0 [<000000000315bc18>] 0xffffffdf052a6488 [<00000000f9dc55b5>] kunit_try_run_case+0x13c/0x3ac [<00000000175a3fd4>] kunit_generic_run_threadfn_adapter+0x80/0xec [<00000000f505065d>] kthread+0x2e8/0x374 [<00000000bbfb0e5d>] ret_from_fork+0x10/0x20 unreferenced object 0xffffff80cbfe9e70 (size 16): comm "kunit_try_catch", pid 1658, jiffies 4294914015 hex dump (first 16 bytes): 10 00 00 00 40 00 00 00 80 00 00 00 00 00 00 00 ....@........... backtrace (crc 857f0cb4): [<0000000028c1b3c2>] kmemleak_alloc+0x34/0x40 [<000000001d6ecc87>] __kmalloc_noprof+0x2bc/0x3c0 [<00000000393795c1>] devm_iio_init_iio_gts+0x4b4/0x16f4 [<0000000071bb4b09>] 0xffffffdf052a62e0 [<000000007d089d45>] 0xffffffdf052a6864 [<00000000f9dc55b5>] kunit_try_run_case+0x13c/0x3ac [<00000000175a3fd4>] kunit_generic_run_threadfn_adapter+0x80/0xec [<00000000f505065d>] kthread+0x2e8/0x374 [<00000000bbfb0e5d>] ret_from_fork+0x10/0x20 ...... It includes 5*5 times "size 64" memory leaks, which correspond to 5 times test_init_iio_gain_scale() calls with gts_test_gains size 10 (10*size(int)) and gts_test_itimes size 5. It also includes 5*1 times "size 16" memory leak, which correspond to one time __test_init_iio_gain_scale() call with gts_test_gains_gain_low size 3 (3*size(int)) and gts_test_itimes size 5. The reason is that the per_time_gains[i] is not freed which is allocated in the "gts->num_itime" for loop in iio_gts_build_avail_scale_table(). Cc: stable@vger.kernel.org Fixes: 38416c28e168 ("iio: light: Add gain-time-scale helpers") Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com> Link: https://patch.msgid.link/20241011095512.3667549-1-ruanjinjie@huawei.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
2024-10-19fs: add file_refChristian Brauner
As atomic_inc_not_zero() is implemented with a try_cmpxchg() loop it has O(N^2) behaviour under contention with N concurrent operations and it is in a hot path in __fget_files_rcu(). The rcuref infrastructures remedies this problem by using an unconditional increment relying on safe- and dead zones to make this work and requiring rcu protection for the data structure in question. This not just scales better it also introduces overflow protection. However, in contrast to generic rcuref, files require a memory barrier and thus cannot rely on *_relaxed() atomic operations and also require to be built on atomic_long_t as having massive amounts of reference isn't unheard of even if it is just an attack. As suggested by Linus, add a file specific variant instead of making this a generic library. Files are SLAB_TYPESAFE_BY_RCU and thus don't have "regular" rcu protection. In short, freeing of files isn't delayed until a grace period has elapsed. Instead, they are freed immediately and thus can be reused (multiple times) within the same grace period. So when picking a file from the file descriptor table via its file descriptor number it is thus possible to see an elevated reference count on file->f_count even though the file has already been recycled possibly multiple times by another task. To guard against this the vfs will pick the file from the file descriptor table twice. Once before the refcount increment and once after to compare the pointers (grossly simplified). If they match then the file is still valid. If not the caller needs to fput() it. The unconditional increment makes the following race possible as illustrated by rcuref: > Deconstruction race > =================== > > The release operation must be protected by prohibiting a grace period in > order to prevent a possible use after free: > > T1 T2 > put() get() > // ref->refcnt = ONEREF > if (!atomic_add_negative(-1, &ref->refcnt)) > return false; <- Not taken > > // ref->refcnt == NOREF > --> preemption > // Elevates ref->refcnt to ONEREF > if (!atomic_add_negative(1, &ref->refcnt)) > return true; <- taken > > if (put(&p->ref)) { <-- Succeeds > remove_pointer(p); > kfree_rcu(p, rcu); > } > > RCU grace period ends, object is freed > > atomic_cmpxchg(&ref->refcnt, NOREF, DEAD); <- UAF > > [...] it prevents the grace period which keeps the object alive until > all put() operations complete. Having files by SLAB_TYPESAFE_BY_RCU shouldn't cause any problems for this deconstruction race. Afaict, the only interesting case would be someone freeing the file and someone immediately recycling it within the same grace period and reinitializing file->f_count to ONEREF while a concurrent fput() is doing atomic_cmpxchg(&ref->refcnt, NOREF, DEAD) as in the race above. But this is safe from SLAB_TYPESAFE_BY_RCU's perspective and it should be safe from rcuref's perspective. T1 T2 T3 fput() fget() // f_count->refcnt = ONEREF if (!atomic_add_negative(-1, &f_count->refcnt)) return false; <- Not taken // f_count->refcnt == NOREF --> preemption // Elevates f_count->refcnt to ONEREF if (!atomic_add_negative(1, &f_count->refcnt)) return true; <- taken if (put(&f_count)) { <-- Succeeds remove_pointer(p); /* * Cache is SLAB_TYPESAFE_BY_RCU * so this is freed without a grace period. */ kmem_cache_free(p); } kmem_cache_alloc() init_file() { // Sets f_count->refcnt to ONEREF rcuref_long_init(&f->f_count, 1); } Object has been reused within the same grace period via kmem_cache_alloc()'s SLAB_TYPESAFE_BY_RCU. /* * With SLAB_TYPESAFE_BY_RCU this would be a safe UAF access and * it would work correctly because the atomic_cmpxchg() * will fail because the refcount has been reset to ONEREF by T3. */ atomic_cmpxchg(&ref->refcnt, NOREF, DEAD); <- UAF However, there are other cases to consider: (1) Benign race due to multiple atomic_long_read() CPU1 CPU2 file_ref_put() // last reference // => count goes negative/FILE_REF_NOREF atomic_long_add_negative_release(-1, &ref->refcnt) -> __file_ref_put() file_ref_get() // goes back from negative/FILE_REF_NOREF to 0 // and file_ref_get() succeeds atomic_long_add_negative(1, &ref->refcnt) // This is immediately followed by file_ref_put() // managing to set FILE_REF_DEAD file_ref_put() // __file_ref_put() continues and sees // cnt > FILE_REF_RELEASED // and splats with // "imbalanced put on file reference count" cnt = atomic_long_read(&ref->refcnt); The race however is benign and the problem is the atomic_long_read(). Instead of performing a separate read this uses atomic_long_dec_return() and pass the value to __file_ref_put(). Thanks to Linus for pointing out that braino. (2) SLAB_TYPESAFE_BY_RCU may cause recycled files to be marked dead When a file is recycled the following race exists: CPU1 CPU2 // @file is already dead and thus // cnt >= FILE_REF_RELEASED. file_ref_get(file) atomic_long_add_negative(1, &ref->refcnt) // We thus call into __file_ref_get() -> __file_ref_get() // which sees cnt >= FILE_REF_RELEASED cnt = atomic_long_read(&ref->refcnt); // In the meantime @file gets freed kmem_cache_free() // and is immediately recycled file = kmem_cache_zalloc() // and the reference count is reinitialized // and the file alive again in someone // else's file descriptor table file_ref_init(&ref->refcnt, 1); // the __file_ref_get() slowpath now continues // and as it saw earlier that cnt >= FILE_REF_RELEASED // it wants to ensure that we're staying in the middle // of the deadzone and unconditionally sets // FILE_REF_DEAD. // This marks @file dead for CPU2... atomic_long_set(&ref->refcnt, FILE_REF_DEAD); // Caller issues a close() system call to close @file close(fd) file = file_close_fd_locked() filp_flush() // The caller sees that cnt >= FILE_REF_RELEASED // and warns the first time... CHECK_DATA_CORRUPTION(file_count(file) == 0) // and then splats a second time because // __file_ref_put() sees cnt >= FILE_REF_RELEASED file_ref_put(&ref->refcnt); -> __file_ref_put() My initial inclination was to replace the unconditional atomic_long_set() with an atomic_long_try_cmpxchg() but Linus pointed out that: > I think we should just make file_ref_get() do a simple > > return !atomic_long_add_negative(1, &ref->refcnt)); > > and nothing else. Yes, multiple CPU's can race, and you can increment > more than once, but the gap - even on 32-bit - between DEAD and > becoming close to REF_RELEASED is so big that we simply don't care. > That's the point of having a gap. I've been testing this with will-it-scale using fstat() on a machine that Jens gave me access (thank you very much!): processor : 511 vendor_id : AuthenticAMD cpu family : 25 model : 160 model name : AMD EPYC 9754 128-Core Processor and I consistently get a 3-5% improvement on 256+ threads. Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202410151043.5d224a27-oliver.sang@intel.com Closes: https://lore.kernel.org/all/202410151611.f4cd71f2-oliver.sang@intel.com Link: https://lore.kernel.org/r/20241007-brauner-file-rcuref-v2-2-387e24dc9163@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
2024-10-19staging: vchiq_arm: Use devm_kzalloc() for drv_mgmt allocationUmang Jain
The struct drv_mgmt 'mgmt' is currently allocated dynamically using kzalloc(). Unfortunately, it is subjected to memory leaks in the error handling paths of the probe() function. To address this issue, use device resource management helper devm_kzalloc(), to ensure cleanup after the allocation. Cc: stable@vger.kernel.org Fixes: 1c9e16b73166 ("staging: vc04_services: vchiq_arm: Split driver static and runtime data") Signed-off-by: Umang Jain <umang.jain@ideasonboard.com> Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org> Link: https://lore.kernel.org/r/20241016130225.61024-3-umang.jain@ideasonboard.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-10-19staging: vchiq_arm: Use devm_kzalloc() for vchiq_arm_state allocationUmang Jain
The struct vchiq_arm_state 'platform_state' is currently allocated dynamically using kzalloc(). Unfortunately, it is never freed and is subjected to memory leaks in the error handling paths of the probe() function. To address the issue, use device resource management helper devm_kzalloc(), to ensure cleanup after its allocation. Fixes: 71bad7f08641 ("staging: add bcm2708 vchiq driver") Cc: stable@vger.kernel.org Signed-off-by: Umang Jain <umang.jain@ideasonboard.com> Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org> Link: https://lore.kernel.org/r/20241016130225.61024-2-umang.jain@ideasonboard.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-10-18fgraph: Allocate ret_stack_list with proper sizeSteven Rostedt
The ret_stack_list is an array of ret_stack shadow stacks for the function graph usage. When the first function graph is enabled, all tasks in the system get a shadow stack. The ret_stack_list is a 32 element array of pointers to these shadow stacks. It allocates the shadow stack in batches (32 stacks at a time), assigns them to running tasks, and continues until all tasks are covered. When the function graph shadow stack changed from an array of ftrace_ret_stack structures to an array of longs, the allocation of ret_stack_list went from allocating an array of 32 elements to just a block defined by SHADOW_STACK_SIZE. Luckily, that's defined as PAGE_SIZE and is much more than enough to hold 32 pointers. But it is way overkill for the amount needed to allocate. Change the allocation of ret_stack_list back to a kcalloc() of FTRACE_RETSTACK_ALLOC_SIZE pointers. Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/20241018215212.23f13f40@rorschach Fixes: 42675b723b484 ("function_graph: Convert ret_stack to a series of longs") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-10-18fgraph: Use CPU hotplug mechanism to initialize idle shadow stacksSteven Rostedt
The function graph infrastructure allocates a shadow stack for every task when enabled. This includes the idle tasks. The first time the function graph is invoked, the shadow stacks are created and never freed until the task exits. This includes the idle tasks. Only the idle tasks that were for online CPUs had their shadow stacks created when function graph tracing started. If function graph tracing is enabled and a CPU comes online, the idle task representing that CPU will not have its shadow stack created, and all function graph tracing for that idle task will be silently dropped. Instead, use the CPU hotplug mechanism to allocate the idle shadow stacks. This will include idle tasks for CPUs that come online during tracing. This issue can be reproduced by: # cd /sys/kernel/tracing # echo 0 > /sys/devices/system/cpu/cpu1/online # echo 0 > set_ftrace_pid # echo function_graph > current_tracer # echo 1 > options/funcgraph-proc # echo 1 > /sys/devices/system/cpu/cpu1 # grep '<idle>' per_cpu/cpu1/trace | head Before, nothing would show up. After: 1) <idle>-0 | 0.811 us | __enqueue_entity(); 1) <idle>-0 | 5.626 us | } /* enqueue_entity */ 1) <idle>-0 | | dl_server_update_idle_time() { 1) <idle>-0 | | dl_scaled_delta_exec() { 1) <idle>-0 | 0.450 us | arch_scale_cpu_capacity(); 1) <idle>-0 | 1.242 us | } 1) <idle>-0 | 1.908 us | } 1) <idle>-0 | | dl_server_start() { 1) <idle>-0 | | enqueue_dl_entity() { 1) <idle>-0 | | task_contending() { Note, if tracing stops and restarts, the old way would then initialize the onlined CPUs. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/20241018214300.6df82178@rorschach Fixes: 868baf07b1a25 ("ftrace: Fix memory leak with function graph and cpu hotplug") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-10-18Merge tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpfLinus Torvalds
Pull bpf fixes from Daniel Borkmann: - Fix BPF verifier to not affect subreg_def marks in its range propagation (Eduard Zingerman) - Fix a truncation bug in the BPF verifier's handling of coerce_reg_to_size_sx (Dimitar Kanaliev) - Fix the BPF verifier's delta propagation between linked registers under 32-bit addition (Daniel Borkmann) - Fix a NULL pointer dereference in BPF devmap due to missing rxq information (Florian Kauer) - Fix a memory leak in bpf_core_apply (Jiri Olsa) - Fix an UBSAN-reported array-index-out-of-bounds in BTF parsing for arrays of nested structs (Hou Tao) - Fix build ID fetching where memory areas backing the file were created with memfd_secret (Andrii Nakryiko) - Fix BPF task iterator tid filtering which was incorrectly using pid instead of tid (Jordan Rome) - Several fixes for BPF sockmap and BPF sockhash redirection in combination with vsocks (Michal Luczaj) - Fix riscv BPF JIT and make BPF_CMPXCHG fully ordered (Andrea Parri) - Fix riscv BPF JIT under CONFIG_CFI_CLANG to prevent the possibility of an infinite BPF tailcall (Pu Lehui) - Fix a build warning from resolve_btfids that bpf_lsm_key_free cannot be resolved (Thomas Weißschuh) - Fix a bug in kfunc BTF caching for modules where the wrong BTF object was returned (Toke Høiland-Jørgensen) - Fix a BPF selftest compilation error in cgroup-related tests with musl libc (Tony Ambardar) - Several fixes to BPF link info dumps to fill missing fields (Tyrone Wu) - Add BPF selftests for kfuncs from multiple modules, checking that the correct kfuncs are called (Simon Sundberg) - Ensure that internal and user-facing bpf_redirect flags don't overlap (Toke Høiland-Jørgensen) - Switch to use kvzmalloc to allocate BPF verifier environment (Rik van Riel) - Use raw_spinlock_t in BPF ringbuf to fix a sleep in atomic splat under RT (Wander Lairson Costa) * tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf: (38 commits) lib/buildid: Handle memfd_secret() files in build_id_parse() selftests/bpf: Add test case for delta propagation bpf: Fix print_reg_state's constant scalar dump bpf: Fix incorrect delta propagation between linked registers bpf: Properly test iter/task tid filtering bpf: Fix iter/task tid filtering riscv, bpf: Make BPF_CMPXCHG fully ordered bpf, vsock: Drop static vsock_bpf_prot initialization vsock: Update msg_count on read_skb() vsock: Update rx_bytes on read_skb() bpf, sockmap: SK_DROP on attempted redirects of unsupported af_vsock selftests/bpf: Add asserts for netfilter link info bpf: Fix link info netfilter flags to populate defrag flag selftests/bpf: Add test for sign extension in coerce_subreg_to_size_sx() selftests/bpf: Add test for truncation after sign extension in coerce_reg_to_size_sx() bpf: Fix truncation bug in coerce_reg_to_size_sx() selftests/bpf: Assert link info uprobe_multi count & path_size if unset bpf: Fix unpopulated path_size when uprobe_multi fields unset selftests/bpf: Fix cross-compiling urandom_read selftests/bpf: Add test for kfunc module order ...
2024-10-18Merge tag 'linux_kselftest-fixes-6.12-rc4' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest Pull kselftest fix from Shuah Khan: - fix test makefile to install tests directory without which the test fails with errors * tag 'linux_kselftest-fixes-6.12-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest: selftest: hid: add the missing tests directory
2024-10-18Input: zinitix - don't fail if linux,keycodes prop is absentNikita Travkin
When initially adding the touchkey support, a mistake was made in the property parsing code. The possible negative errno from device_property_count_u32() was never checked, which was an oversight left from converting to it from the of_property as part of the review fixes. Re-add the correct handling of the absent property, in which case zero touchkeys should be assumed, which would disable the feature. Reported-by: Jakob Hauser <jahau@rocketmail.com> Tested-by: Jakob Hauser <jahau@rocketmail.com> Fixes: 075d9b22c8fe ("Input: zinitix - add touchkey support") Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Nikita Travkin <nikita@trvn.ru> Tested-by: Yassine Oudjana <y.oudjana@protonmail.com> Link: https://lore.kernel.org/r/20241004-zinitix-no-keycodes-v2-1-876dc9fea4b6@trvn.ru Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
2024-10-18Merge tag 'block-6.12-20241018' of git://git.kernel.dk/linuxLinus Torvalds
Pull block fixes from Jens Axboe: - NVMe pull request via Keith: - Fix target passthrough identifier (Nilay) - Fix tcp locking (Hannes) - Replace list with sbitmap for tracking RDMA rsp tags (Guixen) - Remove unnecessary fallthrough statements (Tokunori) - Remove ready-without-media support (Greg) - Fix multipath partition scan deadlock (Keith) - Fix concurrent PCI reset and remove queue mapping (Maurizio) - Fabrics shutdown fixes (Nilay) - Fix for a kerneldoc warning (Keith) - Fix a race with blk-rq-qos and wakeups (Omar) - Cleanup of checking for always-set tag_set (SurajSonawane2415) - Fix for a crash with CPU hotplug notifiers (Ming) - Don't allow zero-copy ublk on unprivileged device (Ming) - Use array_index_nospec() for CDROM (Josh) - Remove dead code in drbd (David) - Tweaks to elevator loading (Breno) * tag 'block-6.12-20241018' of git://git.kernel.dk/linux: cdrom: Avoid barrier_nospec() in cdrom_ioctl_media_changed() nvme: use helper nvme_ctrl_state in nvme_keep_alive_finish function nvme: make keep-alive synchronous operation nvme-loop: flush off pending I/O while shutting down loop controller nvme-pci: fix race condition between reset and nvme_dev_disable() ublk: don't allow user copy for unprivileged device blk-rq-qos: fix crash on rq_qos_wait vs. rq_qos_wake_function race nvme-multipath: defer partition scanning blk-mq: setup queue ->tag_set before initializing hctx elevator: Remove argument from elevator_find_get elevator: do not request_module if elevator exists drbd: Remove unused conn_lowest_minor nvme: disable CC.CRIME (NVME_CC_CRIME) nvme: delete unnecessary fallthru comment nvmet-rdma: use sbitmap to replace rsp free list block: Fix elevator_get_default() checking for NULL q->tag_set nvme: tcp: avoid race between queue_lock lock and destroy nvmet-passthru: clear EUID/NGUID/UUID while using loop target block: fix blk_rq_map_integrity_sg kernel-doc
2024-10-18Merge tag 'io_uring-6.12-20241018' of git://git.kernel.dk/linuxLinus Torvalds
Pull io_uring fixes from Jens Axboe: - Fix a regression this merge window where cloning of registered buffers didn't take into account the dummy_ubuf - Fix a race with reading how many SQRING entries are available, causing userspace to need to loop around io_uring_sqring_wait() rather than being able to rely on SQEs being available when it returned - Ensure that the SQPOLL thread is TASK_RUNNING before running task_work off the cancelation exit path * tag 'io_uring-6.12-20241018' of git://git.kernel.dk/linux: io_uring/sqpoll: ensure task state is TASK_RUNNING when running task_work io_uring/rsrc: ignore dummy_ubuf for buffer cloning io_uring/sqpoll: close race on waiting for sqring entries
2024-10-18ufs: Convert ufs_change_blocknr() to take a folioMatthew Wilcox (Oracle)
Now that ufs_new_fragments() has a folio, pass it to ufs_change_blocknr() as a folio instead of converting it from folio to page to folio. This removes the last use of struct page in UFS. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: Pass a folio to ufs_new_fragments()Matthew Wilcox (Oracle)
All callers now have a folio, pass it to ufs_new_fragments() instead of converting back to a page. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: Convert ufs_inode_getfrag() to take a folioMatthew Wilcox (Oracle)
Pass bh->b_folio instead of bh->b_page. They're in a union, so no code change expected. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: Convert ufs_extend_tail() to take a folioMatthew Wilcox (Oracle)
Pass bh->b_folio instead of bh->b_page. They're in a union, so no code change expected. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: Convert ufs_inode_getblock() to take a folioMatthew Wilcox (Oracle)
Pass bh->b_folio instead of bh->b_page. They're in a union, so no code change expected. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: take the handling of free block counters into a helperAl Viro
There are 3 places where those counters (many and varied...) are adjusted - when we are freeing fragments and get an entire block freed, when we are freeing blocks and (in opposite direction) when we are grabbing a block. The logics is identical (modulo the sign of adjustment) in all three; better take it into a helper - less duplication and less clutter in the callers that way. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18clean ufs_trunc_direct() up a bit...Al Viro
For short files (== no indirect blocks needed) UFS allows the last block to be a partial one. That creates some complications for truncation down to "short file" lengths. ufs_trunc_direct() is called when we'd already made sure that new EOF is not in a hole; nothing needs to be done if we are extending the file and in case we are shrinking the file it needs to * shrink or free the old final block. * free all full direct blocks between the new and old EOF. * possibly shrink the new final block. The logics is needlessly complicated by trying to keep all cases handled by the same sequence of operations. if not shrinking nothing to do else if number of full blocks unchanged free the tail of possibly partial last block else free the tail of (currently full) new last block free all present (full) blocks in between free the (possibly partial) old last block is easier to follow than the result of trying to unify these cases. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: get rid of ubh_{ubhcpymem,memcpyubh}()Al Viro
used only in ufs_read_cylinder_structures()/ufs_put_super_internal() and there we can just as well avoid bothering with ufs_buffer_head and just deal with it fragment-by-fragment. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs_inode_getfrag(): remove junk commentAl Viro
It used to be a stubbed out beginning of ufs2 support, which had been implemented differently quite a while ago. Remove the commented-out (pseudo-)code. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs_free_fragments(): fix the braino in sanity checkAl Viro
The function expects that all fragments it's been asked to free will be within the same block. And it even has a sanity check verifying that - it takes the fragment number modulo the number of fragments per block, adds the count and checks if that's too high. Unfortunately, it misspells the upper limit - instead of ->s_fpb (fragments per block) it says ->s_fpg (fragments per cylinder group). So "too high" ends up being insanely lenient. Had been that way since 2.1.112, when UFS write support had been added. 27 years to spot a typo... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs_clusteracct(): switch to passing fragment numberAl Viro
Currently all callers pass it a block number. All of them have it derived from a fragment number (both fragment and block numbers are within a cylinder group, and thus 32bit). Pass it the fragment number instead; none of the callers has other uses for the block number, so that ends up with cleaner code. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2024-10-18ufs: untangle ubh_...block...(), part 3Al Viro
Pass fragment number instead of a block one. It's available in all callers and it makes the logics inside those helpers much simpler. The bitmap they operate upon is with bit per fragment, block being an aligned group of 1, 2, 4 or 8 adjacent fragments. We still need a switch by the number of fragments in block (== number of bits to check/set/clear), but finding the byte we need to work with becomes uniform and that makes the things easier to follow. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>