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2016-06-30Merge branch 'd_real' of ↵Al Viro
git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs into work.misc
2016-06-15debugfs: open_proxy_open(): avoid double fops releaseNicolai Stange
Debugfs' open_proxy_open(), the ->open() installed at all inodes created through debugfs_create_file_unsafe(), - grabs a reference to the original file_operations instance passed to debugfs_create_file_unsafe() via fops_get(), - installs it at the file's ->f_op by means of replace_fops() - and calls fops_put() on it. Since the semantics of replace_fops() are such that the reference's ownership is transferred, the subsequent fops_put() will result in a double release when the file is eventually closed. Currently, this is not an issue since fops_put() basically does a module_put() on the file_operations' ->owner only and there don't exist any modules calling debugfs_create_file_unsafe() yet. This is expected to change in the future though, c.f. commit c64688081490 ("debugfs: add support for self-protecting attribute file fops"). Remove the call to fops_put() from open_proxy_open(). Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open") Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-06-15debugfs: full_proxy_open(): free proxy on ->open() failureNicolai Stange
Debugfs' full_proxy_open(), the ->open() installed at all inodes created through debugfs_create_file(), - grabs a reference to the original struct file_operations instance passed to debugfs_create_file(), - dynamically allocates a proxy struct file_operations instance wrapping the original - and installs this at the file's ->f_op. Afterwards, it calls the original ->open() and passes its return value back to the VFS layer. Now, if that return value indicates failure, the VFS layer won't ever call ->release() and thus, neither the reference to the original file_operations nor the memory for the proxy file_operations will get released, i.e. both are leaked. Upon failure of the original fops' ->open(), undo the proxy installation. That is: - Set the struct file ->f_op to what it had been when full_proxy_open() was entered. - Drop the reference to the original file_operations. - Free the memory holding the proxy file_operations. Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data") Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-05-29debugfs: ->d_parent is never NULL or negativeAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-04-19Merge 4.6-rc4 into driver-core-nextGreg Kroah-Hartman
We want those fixes in here as well. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: Make automount point inodes permanently emptySeth Forshee
Starting with 4.1 the tracing subsystem has its own filesystem which is automounted in the tracing subdirectory of debugfs. Prior to this debugfs could be bind mounted in a cloned mount namespace, but if tracefs has been mounted under debugfs this now fails because there is a locked child mount. This creates a regression for container software which bind mounts debugfs to satisfy the assumption of some userspace software. In other pseudo filesystems such as proc and sysfs we're already creating mountpoints like this in such a way that no dirents can be created in the directories, allowing them to be exceptions to some MNT_LOCKED tests. In fact we're already do this for the tracefs mountpoint in sysfs. Do the same in debugfs_create_automount(), since the intention here is clearly to create a mountpoint. This fixes the regression, as locked child mounts on permanently empty directories do not cause a bind mount to fail. Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Seth Forshee <seth.forshee@canonical.com> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: unproxify files created through debugfs_create_u32_array()Nicolai Stange
The struct file_operations u32_array_fops associated with files created through debugfs_create_u32_array() has been lifetime aware already: everything needed for subsequent operation is copied to a ->f_private buffer at file opening time in u32_array_open(). Now, ->open() is always protected against file removal issues by the debugfs core. There is no need for the debugfs core to wrap the u32_array_fops with a file lifetime managing proxy. Make debugfs_create_u32_array() create its files in non-proxying operation mode by means of debugfs_create_file_unsafe(). Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: unproxify files created through debugfs_create_blob()Nicolai Stange
Currently, the struct file_operations fops_blob associated with files created through the debugfs_create_blob() helpers are not file lifetime aware. Thus, a lifetime managing proxy is created around fops_blob each time such a file is opened which is an unnecessary waste of resources. Implement file lifetime management for the fops_bool file_operations. Namely, make read_file_blob() safe gainst file removals by means of debugfs_use_file_start() and debugfs_use_file_finish(). Make debugfs_create_blob() create its files in non-proxying operation mode by means of debugfs_create_file_unsafe(). Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: unproxify files created through debugfs_create_bool()Nicolai Stange
Currently, the struct file_operations fops_bool associated with files created through the debugfs_create_bool() helpers are not file lifetime aware. Thus, a lifetime managing proxy is created around fops_bool each time such a file is opened which is an unnecessary waste of resources. Implement file lifetime management for the fops_bool file_operations. Namely, make debugfs_read_file_bool() and debugfs_write_file_bool() safe against file removals by means of debugfs_use_file_start() and debugfs_use_file_finish(). Make debugfs_create_bool() create its files in non-proxying operation mode through debugfs_create_mode_unsafe(). Finally, purge debugfs_create_mode() as debugfs_create_bool() had been its last user. Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: unproxify integer attribute filesNicolai Stange
Currently, the struct file_operations associated with the integer attribute style files created through the debugfs_create_*() helpers are not file lifetime aware as they are defined by means of DEFINE_SIMPLE_ATTRIBUTE(). Thus, a lifetime managing proxy is created around the original fops each time such a file is opened which is an unnecessary waste of resources. Migrate all usages of DEFINE_SIMPLE_ATTRIBUTE() within debugfs itself to DEFINE_DEBUGFS_ATTRIBUTE() in order to implement file lifetime managing within the struct file_operations thus defined. Introduce the debugfs_create_mode_unsafe() helper, analogous to debugfs_create_mode(), but distinct in that it creates the files in non-proxying operation mode through debugfs_create_file_unsafe(). Feed all struct file_operations migrated to DEFINE_DEBUGFS_ATTRIBUTE() into debugfs_create_mode_unsafe() instead of former debugfs_create_mode(). Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: add support for self-protecting attribute file fopsNicolai Stange
In order to protect them against file removal issues, debugfs_create_file() creates a lifetime managing proxy around each struct file_operations handed in. In cases where this struct file_operations is able to manage file lifetime by itself already, the proxy created by debugfs is a waste of resources. The most common class of struct file_operations given to debugfs are those defined by means of the DEFINE_SIMPLE_ATTRIBUTE() macro. Introduce a DEFINE_DEBUGFS_ATTRIBUTE() macro to allow any struct file_operations of this class to be easily made file lifetime aware and thus, to be operated unproxied. Specifically, introduce debugfs_attr_read() and debugfs_attr_write() which wrap simple_attr_read() and simple_attr_write() under the protection of a debugfs_use_file_start()/debugfs_use_file_finish() pair. Make DEFINE_DEBUGFS_ATTRIBUTE() set the defined struct file_operations' ->read() and ->write() members to these wrappers. Export debugfs_create_file_unsafe() in order to allow debugfs users to create their files in non-proxying operation mode. Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: prevent access to removed files' private dataNicolai Stange
Upon return of debugfs_remove()/debugfs_remove_recursive(), it might still be attempted to access associated private file data through previously opened struct file objects. If that data has been freed by the caller of debugfs_remove*() in the meanwhile, the reading/writing process would either encounter a fault or, if the memory address in question has been reassigned again, unrelated data structures could get overwritten. However, since debugfs files are seldomly removed, usually from module exit handlers only, the impact is very low. Currently, there are ~1000 call sites of debugfs_create_file() spread throughout the whole tree and touching all of those struct file_operations in order to make them file removal aware by means of checking the result of debugfs_use_file_start() from within their methods is unfeasible. Instead, wrap the struct file_operations by a lifetime managing proxy at file open: - In debugfs_create_file(), the original fops handed in has got stashed away in ->d_fsdata already. - In debugfs_create_file(), install a proxy file_operations factory, debugfs_full_proxy_file_operations, at ->i_fop. This proxy factory has got an ->open() method only. It carries out some lifetime checks and if successful, dynamically allocates and sets up a new struct file_operations proxy at ->f_op. Afterwards, it forwards to the ->open() of the original struct file_operations in ->d_fsdata, if any. The dynamically set up proxy at ->f_op has got a lifetime managing wrapper set for each of the methods defined in the original struct file_operations in ->d_fsdata. Its ->release()er frees the proxy again and forwards to the original ->release(), if any. In order not to mislead the VFS layer, it is strictly necessary to leave those fields blank in the proxy that have been NULL in the original struct file_operations also, i.e. aren't supported. This is why there is a need for dynamically allocated proxies. The choice made not to allocate a proxy instance for every dentry at file creation, but for every struct file object instantiated thereof is justified by the expected usage pattern of debugfs, namely that in general very few files get opened more than once at a time. The wrapper methods set in the struct file_operations implement lifetime managing by means of the SRCU protection facilities already in place for debugfs: They set up a SRCU read side critical section and check whether the dentry is still alive by means of debugfs_use_file_start(). If so, they forward the call to the original struct file_operation stored in ->d_fsdata, still under the protection of the SRCU read side critical section. This SRCU read side critical section prevents any pending debugfs_remove() and friends to return to their callers. Since a file's private data must only be freed after the return of debugfs_remove(), the ongoing proxied call is guarded against any file removal race. If, on the other hand, the initial call to debugfs_use_file_start() detects that the dentry is dead, the wrapper simply returns -EIO and does not forward the call. Note that the ->poll() wrapper is special in that its signature does not allow for the return of arbitrary -EXXX values and thus, POLLHUP is returned here. In order not to pollute debugfs with wrapper definitions that aren't ever needed, I chose not to define a wrapper for every struct file_operations method possible. Instead, a wrapper is defined only for the subset of methods which are actually set by any debugfs users. Currently, these are: ->llseek() ->read() ->write() ->unlocked_ioctl() ->poll() The ->release() wrapper is special in that it does not protect the original ->release() in any way from dead files in order not to leak resources. Thus, any ->release() handed to debugfs must implement file lifetime management manually, if needed. For only 33 out of a total of 434 releasers handed in to debugfs, it could not be verified immediately whether they access data structures that might have been freed upon a debugfs_remove() return in the meanwhile. Export debugfs_use_file_start() and debugfs_use_file_finish() in order to allow any ->release() to manually implement file lifetime management. For a set of common cases of struct file_operations implemented by the debugfs_core itself, future patches will incorporate file lifetime management directly within those in order to allow for their unproxied operation. Rename the original, non-proxying "debugfs_create_file()" to "debugfs_create_file_unsafe()" and keep it for future internal use by debugfs itself. Factor out code common to both into the new __debugfs_create_file(). Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-04-12debugfs: prevent access to possibly dead file_operations at file openNicolai Stange
Nothing prevents a dentry found by path lookup before a return of __debugfs_remove() to actually get opened after that return. Now, after the return of __debugfs_remove(), there are no guarantees whatsoever regarding the memory the corresponding inode's file_operations object had been kept in. Since __debugfs_remove() is seldomly invoked, usually from module exit handlers only, the race is hard to trigger and the impact is very low. A discussion of the problem outlined above as well as a suggested solution can be found in the (sub-)thread rooted at http://lkml.kernel.org/g/20130401203445.GA20862@ZenIV.linux.org.uk ("Yet another pipe related oops.") Basically, Greg KH suggests to introduce an intermediate fops and Al Viro points out that a pointer to the original ones may be stored in ->d_fsdata. Follow this line of reasoning: - Add SRCU as a reverse dependency of DEBUG_FS. - Introduce a srcu_struct object for the debugfs subsystem. - In debugfs_create_file(), store a pointer to the original file_operations object in ->d_fsdata. - Make debugfs_remove() and debugfs_remove_recursive() wait for a SRCU grace period after the dentry has been delete()'d and before they return to their callers. - Introduce an intermediate file_operations object named "debugfs_open_proxy_file_operations". It's ->open() functions checks, under the protection of a SRCU read lock, whether the dentry is still alive, i.e. has not been d_delete()'d and if so, tries to acquire a reference on the owning module. On success, it sets the file object's ->f_op to the original file_operations and forwards the ongoing open() call to the original ->open(). - For clarity, rename the former debugfs_file_operations to debugfs_noop_file_operations -- they are in no way canonical. The choice of SRCU over "normal" RCU is justified by the fact, that the former may also be used to protect ->i_private data from going away during the execution of a file's readers and writers which may (and do) sleep. Finally, introduce the fs/debugfs/internal.h header containing some declarations internal to the debugfs implementation. Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-03-29fs: debugfs: Replace CURRENT_TIME by current_fs_time()Deepa Dinamani
CURRENT_TIME macro is not appropriate for filesystems as it doesn't use the right granularity for filesystem timestamps. Use current_fs_time() instead. Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-03-29debugfs: fix inode i_nlink references for automount dentryRoman Pen
Directory inodes should start off with i_nlink == 2 (one extra ref for "." entry). debugfs_create_automount() increases neither the i_nlink reference for current inode nor for parent inode. On attempt to remove the automount dentry, kernel complains: [ 86.288070] WARNING: CPU: 1 PID: 3616 at fs/inode.c:273 drop_nlink+0x3e/0x50() [ 86.288461] Modules linked in: debugfs_example2(O-) [ 86.288745] CPU: 1 PID: 3616 Comm: rmmod Tainted: G O 4.4.0-rc3-next-20151207+ #135 [ 86.289197] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.2-20150617_082717-anatol 04/01/2014 [ 86.289696] ffffffff81be05c9 ffff8800b9e6fda0 ffffffff81352e2c 0000000000000000 [ 86.290110] ffff8800b9e6fdd8 ffffffff81065142 ffff8801399175e8 ffff8800bb78b240 [ 86.290507] ffff8801399175e8 ffff8800b73d7898 ffff8800b73d7840 ffff8800b9e6fde8 [ 86.290933] Call Trace: [ 86.291080] [<ffffffff81352e2c>] dump_stack+0x4e/0x82 [ 86.291340] [<ffffffff81065142>] warn_slowpath_common+0x82/0xc0 [ 86.291640] [<ffffffff8106523a>] warn_slowpath_null+0x1a/0x20 [ 86.291932] [<ffffffff811ae62e>] drop_nlink+0x3e/0x50 [ 86.292208] [<ffffffff811ba35b>] simple_unlink+0x4b/0x60 [ 86.292481] [<ffffffff811ba3a7>] simple_rmdir+0x37/0x50 [ 86.292748] [<ffffffff812d9808>] __debugfs_remove.part.16+0xa8/0xd0 [ 86.293082] [<ffffffff812d9a0b>] debugfs_remove_recursive+0xdb/0x1c0 [ 86.293406] [<ffffffffa00004dd>] cleanup_module+0x2d/0x3b [debugfs_example2] [ 86.293762] [<ffffffff810d959b>] SyS_delete_module+0x16b/0x220 [ 86.294077] [<ffffffff818ef857>] entry_SYSCALL_64_fastpath+0x12/0x6a [ 86.294405] ---[ end trace c9fc53353fe14a36 ]--- [ 86.294639] ------------[ cut here ]------------ To reproduce the issue it is enough to invoke these lines: autom = debugfs_create_automount("automount", NULL, vfsmount_cb, data); BUG_ON(IS_ERR_OR_NULL(autom)); debugfs_remove(autom); The issue is fixed by increasing inode i_nlink references for current and parent inodes. Signed-off-by: Roman Pen <r.peniaev@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-01-22wrappers for ->i_mutex accessAl Viro
parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested}, inode_foo(inode) being mutex_foo(&inode->i_mutex). Please, use those for access to ->i_mutex; over the coming cycle ->i_mutex will become rwsem, with ->lookup() done with it held only shared. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-11-11debugfs: fix refcount imbalance in start_creatingDaniel Borkmann
In debugfs' start_creating(), we pin the file system to safely access its root. When we failed to create a file, we unpin the file system via failed_creating() to release the mount count and eventually the reference of the vfsmount. However, when we run into an error during lookup_one_len() when still in start_creating(), we only release the parent's mutex but not so the reference on the mount. Looks like it was done in the past, but after splitting portions of __create_file() into start_creating() and end_creating() via 190afd81e4a5 ("debugfs: split the beginning and the end of __create_file() off"), this seemed missed. Noticed during code review. Fixes: 190afd81e4a5 ("debugfs: split the beginning and the end of __create_file() off") Cc: stable@vger.kernel.org # v4.0+ Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-10-18debugfs: Add debugfs_create_ulong()Viresh Kumar
Add debugfs_create_ulong() for the users of type 'unsigned long'. These will be 32 bits long on a 32 bit machine and 64 bits long on a 64 bit machine. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17debugfs: Add read-only/write-only bool file opsStephen Boyd
There aren't any read-only or write-only bool file ops, but there is a caller of debugfs_create_bool() that calls it with mode equal to 0400. This leads to the possibility of userspace modifying the file, so let's use the newly created debugfs_create_mode() helper here to fix this. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17debugfs: Add read-only/write-only size_t file opsStephen Boyd
There aren't any read-only or write-only size_t file ops, but there is a caller of debugfs_create_size_t() that calls it with mode equal to 0400. This leads to the possibility of userspace modifying the file, so let's use the newly created debugfs_create_mode() helper here to fix this. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17debugfs: Add read-only/write-only x64 file opsStephen Boyd
There aren't any read-only or write-only x64 file ops, but there is a caller of debugfs_create_x64() that calls it with mode equal to S_IRUGO. This leads to the possibility of userspace modifying the file, so let's use the newly created debugfs_create_mode() helper here to fix this. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-17debugfs: Consolidate file mode checks in debugfs_create_*()Stephen Boyd
The code that creates debugfs file with different file ops based on the file mode is duplicated in each debugfs_create_*() API. Consolidate that code into debugfs_create_mode(), that takes three file ops structures so that we don't have to keep copy/pasting that logic. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-04debugfs: document that debugfs_remove*() accepts NULL and error valuesUlf Magnusson
According to commit a59d6293e537 ("debugfs: change parameter check in debugfs_remove() functions"), this is meant to make cleanup easier for callers. In that case it ought to be documented. Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-10-04debugfs: Pass bool pointer to debugfs_create_bool()Viresh Kumar
Its a bit odd that debugfs_create_bool() takes 'u32 *' as an argument, when all it needs is a boolean pointer. It would be better to update this API to make it accept 'bool *' instead, as that will make it more consistent and often more convenient. Over that bool takes just a byte. That required updates to all user sites as well, in the same commit updating the API. regmap core was also using debugfs_{read|write}_file_bool(), directly and variable types were updated for that to be bool as well. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Mark Brown <broonie@kernel.org> Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-07-20debugfs: Export bool read/write functionsRichard Fitzgerald
The file read/write functions for bools have no special dependencies on debugfs internals and are sufficiently non-trivial to be worth exporting so clients can re-use the implementation. Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Mark Brown <broonie@kernel.org>
2015-07-04Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull more vfs updates from Al Viro: "Assorted VFS fixes and related cleanups (IMO the most interesting in that part are f_path-related things and Eric's descriptor-related stuff). UFS regression fixes (it got broken last cycle). 9P fixes. fs-cache series, DAX patches, Jan's file_remove_suid() work" [ I'd say this is much more than "fixes and related cleanups". The file_table locking rule change by Eric Dumazet is a rather big and fundamental update even if the patch isn't huge. - Linus ] * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (49 commits) 9p: cope with bogus responses from server in p9_client_{read,write} p9_client_write(): avoid double p9_free_req() 9p: forgetting to cancel request on interrupted zero-copy RPC dax: bdev_direct_access() may sleep block: Add support for DAX reads/writes to block devices dax: Use copy_from_iter_nocache dax: Add block size note to documentation fs/file.c: __fget() and dup2() atomicity rules fs/file.c: don't acquire files->file_lock in fd_install() fs:super:get_anon_bdev: fix race condition could cause dev exceed its upper limitation vfs: avoid creation of inode number 0 in get_next_ino namei: make set_root_rcu() return void make simple_positive() public ufs: use dir_pages instead of ufs_dir_pages() pagemap.h: move dir_pages() over there remove the pointless include of lglock.h fs: cleanup slight list_entry abuse xfs: Correctly lock inode when removing suid and file capabilities fs: Call security_ops->inode_killpriv on truncate fs: Provide function telling whether file_remove_privs() will do anything ...
2015-07-03Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull user namespace updates from Eric Biederman: "Long ago and far away when user namespaces where young it was realized that allowing fresh mounts of proc and sysfs with only user namespace permissions could violate the basic rule that only root gets to decide if proc or sysfs should be mounted at all. Some hacks were put in place to reduce the worst of the damage could be done, and the common sense rule was adopted that fresh mounts of proc and sysfs should allow no more than bind mounts of proc and sysfs. Unfortunately that rule has not been fully enforced. There are two kinds of gaps in that enforcement. Only filesystems mounted on empty directories of proc and sysfs should be ignored but the test for empty directories was insufficient. So in my tree directories on proc, sysctl and sysfs that will always be empty are created specially. Every other technique is imperfect as an ordinary directory can have entries added even after a readdir returns and shows that the directory is empty. Special creation of directories for mount points makes the code in the kernel a smidge clearer about it's purpose. I asked container developers from the various container projects to help test this and no holes were found in the set of mount points on proc and sysfs that are created specially. This set of changes also starts enforcing the mount flags of fresh mounts of proc and sysfs are consistent with the existing mount of proc and sysfs. I expected this to be the boring part of the work but unfortunately unprivileged userspace winds up mounting fresh copies of proc and sysfs with noexec and nosuid clear when root set those flags on the previous mount of proc and sysfs. So for now only the atime, read-only and nodev attributes which userspace happens to keep consistent are enforced. Dealing with the noexec and nosuid attributes remains for another time. This set of changes also addresses an issue with how open file descriptors from /proc/<pid>/ns/* are displayed. Recently readlink of /proc/<pid>/fd has been triggering a WARN_ON that has not been meaningful since it was added (as all of the code in the kernel was converted) and is not now actively wrong. There is also a short list of issues that have not been fixed yet that I will mention briefly. It is possible to rename a directory from below to above a bind mount. At which point any directory pointers below the renamed directory can be walked up to the root directory of the filesystem. With user namespaces enabled a bind mount of the bind mount can be created allowing the user to pick a directory whose children they can rename to outside of the bind mount. This is challenging to fix and doubly so because all obvious solutions must touch code that is in the performance part of pathname resolution. As mentioned above there is also a question of how to ensure that developers by accident or with purpose do not introduce exectuable files on sysfs and proc and in doing so introduce security regressions in the current userspace that will not be immediately obvious and as such are likely to require breaking userspace in painful ways once they are recognized" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: vfs: Remove incorrect debugging WARN in prepend_path mnt: Update fs_fully_visible to test for permanently empty directories sysfs: Create mountpoints with sysfs_create_mount_point sysfs: Add support for permanently empty directories to serve as mount points. kernfs: Add support for always empty directories. proc: Allow creating permanently empty directories that serve as mount points sysctl: Allow creating permanently empty directories that serve as mountpoints. fs: Add helper functions for permanently empty directories. vfs: Ignore unlocked mounts in fs_fully_visible mnt: Modify fs_fully_visible to deal with locked ro nodev and atime mnt: Refactor the logic for mounting sysfs and proc in a user namespace
2015-07-01sysfs: Create mountpoints with sysfs_create_mount_pointEric W. Biederman
This allows for better documentation in the code and it allows for a simpler and fully correct version of fs_fully_visible to be written. The mount points converted and their filesystems are: /sys/hypervisor/s390/ s390_hypfs /sys/kernel/config/ configfs /sys/kernel/debug/ debugfs /sys/firmware/efi/efivars/ efivarfs /sys/fs/fuse/connections/ fusectl /sys/fs/pstore/ pstore /sys/kernel/tracing/ tracefs /sys/fs/cgroup/ cgroup /sys/kernel/security/ securityfs /sys/fs/selinux/ selinuxfs /sys/fs/smackfs/ smackfs Cc: stable@vger.kernel.org Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2015-06-23make simple_positive() publicAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-05-10debugfs: switch to simple_follow_link()Al Viro
Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-04-26Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull fourth vfs update from Al Viro: "d_inode() annotations from David Howells (sat in for-next since before the beginning of merge window) + four assorted fixes" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: RCU pathwalk breakage when running into a symlink overmounting something fix I_DIO_WAKEUP definition direct-io: only inc/dec inode->i_dio_count for file systems fs/9p: fix readdir() VFS: assorted d_backing_inode() annotations VFS: fs/inode.c helpers: d_inode() annotations VFS: fs/cachefiles: d_backing_inode() annotations VFS: fs library helpers: d_inode() annotations VFS: assorted weird filesystems: d_inode() annotations VFS: normal filesystems (and lustre): d_inode() annotations VFS: security/: d_inode() annotations VFS: security/: d_backing_inode() annotations VFS: net/: d_inode() annotations VFS: net/unix: d_backing_inode() annotations VFS: kernel/: d_inode() annotations VFS: audit: d_backing_inode() annotations VFS: Fix up some ->d_inode accesses in the chelsio driver VFS: Cachefiles should perform fs modifications on the top layer only VFS: AF_UNIX sockets should call mknod on the top layer only
2015-04-16Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull third hunk of vfs changes from Al Viro: "This contains the ->direct_IO() changes from Omar + saner generic_write_checks() + dealing with fcntl()/{read,write}() races (mirroring O_APPEND/O_DIRECT into iocb->ki_flags and instead of repeatedly looking at ->f_flags, which can be changed by fcntl(2), check ->ki_flags - which cannot) + infrastructure bits for dhowells' d_inode annotations + Christophs switch of /dev/loop to vfs_iter_write()" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (30 commits) block: loop: switch to VFS ITER_BVEC configfs: Fix inconsistent use of file_inode() vs file->f_path.dentry->d_inode VFS: Make pathwalk use d_is_reg() rather than S_ISREG() VFS: Fix up debugfs to use d_is_dir() in place of S_ISDIR() VFS: Combine inode checks with d_is_negative() and d_is_positive() in pathwalk NFS: Don't use d_inode as a variable name VFS: Impose ordering on accesses of d_inode and d_flags VFS: Add owner-filesystem positive/negative dentry checks nfs: generic_write_checks() shouldn't be done on swapout... ocfs2: use __generic_file_write_iter() mirror O_APPEND and O_DIRECT into iocb->ki_flags switch generic_write_checks() to iocb and iter ocfs2: move generic_write_checks() before the alignment checks ocfs2_file_write_iter: stop messing with ppos udf_file_write_iter: reorder and simplify fuse: ->direct_IO() doesn't need generic_write_checks() ext4_file_write_iter: move generic_write_checks() up xfs_file_aio_write_checks: switch to iocb/iov_iter generic_write_checks(): drop isblk argument blkdev_write_iter: expand generic_file_checks() call in there ...
2015-04-15VFS: normal filesystems (and lustre): d_inode() annotationsDavid Howells
that's the bulk of filesystem drivers dealing with inodes of their own Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-04-15VFS: Fix up debugfs to use d_is_dir() in place of S_ISDIR()David Howells
Fix up debugfs to use d_is_dir(dentry) in place of S_ISDIR(dentry->d_inode->i_mode). Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-04-03debugfs: allow bad parent pointers to be passed inGreg KH
If something went wrong with creating a debugfs file/symlink/directory, that value could be passed down into debugfs again as a parent dentry. To make caller code simpler, just error out if this happens, and don't crash the kernel. Reported-by: Alex Elder <elder@linaro.org> Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Alex Elder <elder@linaro.org>
2015-02-22debugfs: leave freeing a symlink body until inode evictionAl Viro
As it is, we have debugfs_remove() racing with symlink traversals. Supply ->evict_inode() and do freeing there - inode will remain pinned until we are done with the symlink body. And rip the idiocy with checking if dentry is positive right after we'd verified debugfs_positive(), which is a stronger check... Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-02-22VFS: (Scripted) Convert S_ISLNK/DIR/REG(dentry->d_inode) to d_is_*(dentry)David Howells
Convert the following where appropriate: (1) S_ISLNK(dentry->d_inode) to d_is_symlink(dentry). (2) S_ISREG(dentry->d_inode) to d_is_reg(dentry). (3) S_ISDIR(dentry->d_inode) to d_is_dir(dentry). This is actually more complicated than it appears as some calls should be converted to d_can_lookup() instead. The difference is whether the directory in question is a real dir with a ->lookup op or whether it's a fake dir with a ->d_automount op. In some circumstances, we can subsume checks for dentry->d_inode not being NULL into this, provided we the code isn't in a filesystem that expects d_inode to be NULL if the dirent really *is* negative (ie. if we're going to use d_inode() rather than d_backing_inode() to get the inode pointer). Note that the dentry type field may be set to something other than DCACHE_MISS_TYPE when d_inode is NULL in the case of unionmount, where the VFS manages the fall-through from a negative dentry to a lower layer. In such a case, the dentry type of the negative union dentry is set to the same as the type of the lower dentry. However, if you know d_inode is not NULL at the call site, then you can use the d_is_xxx() functions even in a filesystem. There is one further complication: a 0,0 chardev dentry may be labelled DCACHE_WHITEOUT_TYPE rather than DCACHE_SPECIAL_TYPE. Strictly, this was intended for special directory entry types that don't have attached inodes. The following perl+coccinelle script was used: use strict; my @callers; open($fd, 'git grep -l \'S_IS[A-Z].*->d_inode\' |') || die "Can't grep for S_ISDIR and co. callers"; @callers = <$fd>; close($fd); unless (@callers) { print "No matches\n"; exit(0); } my @cocci = ( '@@', 'expression E;', '@@', '', '- S_ISLNK(E->d_inode->i_mode)', '+ d_is_symlink(E)', '', '@@', 'expression E;', '@@', '', '- S_ISDIR(E->d_inode->i_mode)', '+ d_is_dir(E)', '', '@@', 'expression E;', '@@', '', '- S_ISREG(E->d_inode->i_mode)', '+ d_is_reg(E)' ); my $coccifile = "tmp.sp.cocci"; open($fd, ">$coccifile") || die $coccifile; print($fd "$_\n") || die $coccifile foreach (@cocci); close($fd); foreach my $file (@callers) { chomp $file; print "Processing ", $file, "\n"; system("spatch", "--sp-file", $coccifile, $file, "--in-place", "--no-show-diff") == 0 || die "spatch failed"; } [AV: overlayfs parts skipped] Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-02-17debugfs: Provide a file creation function that also takes an initial sizeDavid Howells
Provide a file creation function that also takes an initial size so that the caller doesn't have to set i_size, thus meaning that we don't have to call deal with ->d_inode in the callers. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25new primitive: debugfs_create_automount()Al Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25debugfs: split end_creating() into success and failure casesAl Viro
... and don't bother with dput(dentry) in the former and with dget(dentry) preceding all its calls. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25debugfs: take mode-dependent parts of debugfs_get_inode() into callersAl Viro
... and trim the arguments list Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25fold debugfs_mknod() into callersAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25fold debugfs_create() into callerAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25fold debugfs_mkdir() into callerAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25debugfs_mknod(): get rid useless argumentsAl Viro
dev is always zero, dir was only used to get its ->i_sb, which is equal to ->d_sb of dentry... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25fold debugfs_link() into callerAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25debugfs: kill __create_file()Al Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25debugfs: split the beginning and the end of __create_file() offAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2015-01-25debugfs_{mkdir,create,link}(): get rid of redundant argumentAl Viro
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2014-12-14Merge tag 'driver-core-3.19-rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core Pull driver core update from Greg KH: "Here's the set of driver core patches for 3.19-rc1. They are dominated by the removal of the .owner field in platform drivers. They touch a lot of files, but they are "simple" changes, just removing a line in a structure. Other than that, a few minor driver core and debugfs changes. There are some ath9k patches coming in through this tree that have been acked by the wireless maintainers as they relied on the debugfs changes. Everything has been in linux-next for a while" * tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (324 commits) Revert "ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries" fs: debugfs: add forward declaration for struct device type firmware class: Deletion of an unnecessary check before the function call "vunmap" firmware loader: fix hung task warning dump devcoredump: provide a one-way disable function device: Add dev_<level>_once variants ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries ath: use seq_file api for ath9k debugfs files debugfs: add helper function to create device related seq_file drivers/base: cacheinfo: remove noisy error boot message Revert "core: platform: add warning if driver has no owner" drivers: base: support cpu cache information interface to userspace via sysfs drivers: base: add cpu_device_create to support per-cpu devices topology: replace custom attribute macros with standard DEVICE_ATTR* cpumask: factor out show_cpumap into separate helper function driver core: Fix unbalanced device reference in drivers_probe driver core: fix race with userland in device_add() sysfs/kernfs: make read requests on pre-alloc files use the buffer. sysfs/kernfs: allow attributes to request write buffer be pre-allocated. fs: sysfs: return EGBIG on write if offset is larger than file size ...