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Once unix_sock ->path is set, we are guaranteed that its ->path will remain
unchanged (and pinned) until the socket is closed. OTOH, dentry_open()
does not modify the path passed to it.
IOW, there's no need to copy unix_sk(sk)->path in unix_open_file() - we
can just pass it to dentry_open() and be done with that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/20250712054157.GZ1880847@ZenIV
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The combination of spinlock_t lock and seqcount_spinlock_t seq
in struct fs_struct is an open-coded seqlock_t (see linux/seqlock_types.h).
Combine and switch to equivalent seqlock_t primitives. AFAICS,
that does end up with the same sequence of underlying operations in all
cases.
While we are at it, get_fs_pwd() is open-coded verbatim in
get_path_from_fd(); rather than applying conversion to it, replace with
the call of get_fs_pwd() there. Not worth splitting the commit for that,
IMO...
A bit of historical background - conversion of seqlock_t to
use of seqcount_spinlock_t happened several months after the same
had been done to struct fs_struct; switching fs_struct to seqlock_t
could've been done immediately after that, but it looks like nobody
had gotten around to that until now.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://lore.kernel.org/20250702053437.GC1880847@ZenIV
Acked-by: Ahmed S. Darwish <darwi@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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This is a logical continuation of the earlier work to create pidfds for
reaped tasks through the SO_PEERPIDFD socket option merged in
923ea4d4482b ("Merge patch series "net, pidfs: enable handing out pidfds
for reaped sk->sk_peer_pid"").
* patches from https://lore.kernel.org/20250703222314.309967-1-aleksandr.mikhalitsyn@canonical.com:
selftests: net: extend SCM_PIDFD test to cover stale pidfds
af_unix: enable handing out pidfds for reaped tasks in SCM_PIDFD
af_unix: stash pidfs dentry when needed
af_unix/scm: fix whitespace errors
af_unix: introduce and use scm_replace_pid() helper
af_unix: introduce unix_skb_to_scm helper
af_unix: rework unix_maybe_add_creds() to allow sleep
Link: https://lore.kernel.org/20250703222314.309967-1-aleksandr.mikhalitsyn@canonical.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Extend SCM_PIDFD test scenarios to also cover dead task's
pidfd retrieval and reading its exit info.
Cc: linux-kselftest@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: Shuah Khan <shuah@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-8-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Now everything is ready to pass PIDFD_STALE to pidfd_prepare().
This will allow opening pidfd for reaped tasks.
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-7-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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We need to ensure that pidfs dentry is allocated when we meet any
struct pid for the first time. This will allows us to open pidfd
even after the task it corresponds to is reaped.
Basically, we need to identify all places where we fill skb/scm_cookie
with struct pid reference for the first time and call pidfs_register_pid().
Tricky thing here is that we have a few places where this happends
depending on what userspace is doing:
- [__scm_replace_pid()] explicitly sending an SCM_CREDENTIALS message
and specified pid in a numeric format
- [unix_maybe_add_creds()] enabled SO_PASSCRED/SO_PASSPIDFD but
didn't send SCM_CREDENTIALS explicitly
- [scm_send()] force_creds is true. Netlink case, we don't need to touch it.
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-6-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Fix whitespace/formatting errors.
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-5-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Existing logic in __scm_send() related to filling an struct scm_cookie
with a proper struct pid reference is already pretty tricky. Let's
simplify it a bit by introducing a new helper. This helper will be
extended in one of the next patches.
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-4-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Instead of open-coding let's consolidate this logic in a separate
helper. This will simplify further changes.
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-3-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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As a preparation for the next patches we need to allow sleeping
in unix_maybe_add_creds() and also return err. Currently, we can't do
that as unix_maybe_add_creds() is being called under unix_state_lock().
There is no need for this, really. So let's move call sites of
this helper a bit and do necessary function signature changes.
Cc: linux-kernel@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Luca Boccassi <bluca@debian.org>
Cc: David Rheinsberg <david@readahead.eu>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/20250703222314.309967-2-aleksandr.mikhalitsyn@canonical.com
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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on file handle"
Christian Brauner <brauner@kernel.org> says:
Various filesystems such as pidfs and drm support opening file handles
without having to require a file descriptor to identify the filesystem.
The filesystem are global single instances and can be trivially
identified solely on the information encoded in the file handle.
This makes it possible to not have to keep or acquire a sentinal file
descriptor just to pass it to open_by_handle_at() to identify the
filesystem. That's especially useful when such sentinel file descriptor
cannot or should not be acquired.
For pidfs this means a file handle can function as full replacement for
storing a pid in a file. Instead a file handle can be stored and
reopened purely based on the file handle.
Such autonomous file handles can be opened with or without specifying a
a file descriptor. If no proper file descriptor is used the
FD_PIDFS_ROOT sentinel must be passed. This allows us to define further
special negative fd sentinels in the future.
Userspace can trivially test for support by trying to open the file
handle with an invalid file descriptor.
* patches from https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-0-d02a04858fe3@kernel.org:
selftests/pidfd: decode pidfd file handles withou having to specify an fd
fhandle, pidfs: support open_by_handle_at() purely based on file handle
uapi/fcntl: add FD_PIDFS_ROOT
uapi/fcntl: add FD_INVALID
uapi/fcntl: mark range as reserved
fhandle: reflow get_path_anchor()
pidfs: add pidfs_root_path() helper
fhandle: rename to get_path_anchor()
fhandle: hoist copy_from_user() above get_path_from_fd()
fhandle: raise FILEID_IS_DIR in handle_type
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-0-d02a04858fe3@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-11-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Various filesystems such as pidfs (and likely drm in the future) have a
use-case to support opening files purely based on the handle without
having to require a file descriptor to another object. That's especially
the case for filesystems that don't do any lookup whatsoever and there's
zero relationship between the objects. Such filesystems are also
singletons that stay around for the lifetime of the system meaning that
they can be uniquely identified and accessed purely based on the file
handle type. Enable that so that userspace doesn't have to allocate an
object needlessly especially if they can't do that for whatever reason.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-10-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add a special file descriptor indicating the root of the pidfs
filesystem.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add a marker for an invalid file descriptor.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-7-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Don't jump somewhere into the middle of the reserved range. We're still
able to change that value it won't be that widely used yet. If not, we
can revert.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Mark the range from -10000 to -40000 as a range reserved for special
in-kernel values. Move the PIDFD_SELF_*/PIDFD_THREAD_* sentinels over so
all the special values are in one place.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-6-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Switch to a more common coding style.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-5-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Allow to return the root of the global pidfs filesystem.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-4-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Rename as we're going to expand the function in the next step. The path
just serves as the anchor tying the decoding to the filesystem.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-3-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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In follow-up patches we need access to @file_handle->handle_type
before we start caring about get_path_from_fd().
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-2-d02a04858fe3@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Currently FILEID_IS_DIR is raised in fh_flags which is wrong.
Raise it in handle->handle_type were it's supposed to be.
Link: https://lore.kernel.org/20250624-work-pidfs-fhandle-v2-1-d02a04858fe3@kernel.org
Fixes: c374196b2b9f ("fs: name_to_handle_at() support for "explicit connectable" file handles")
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Ensure that we handle the case where task creation fails and pid->attr
was never accessed at all.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Christian Brauner <brauner@kernel.org> says:
Persist exit and coredump information independent of whether anyone
currently holds a pidfd for the struct pid.
The current scheme allocated pidfs dentries on-demand repeatedly.
This scheme is reaching it's limits as it makes it impossible to pin
information that needs to be available after the task has exited or
coredumped and that should not be lost simply because the pidfd got
closed temporarily. The next opener should still see the stashed
information.
This is also a prerequisite for supporting extended attributes on
pidfds to allow attaching meta information to them.
If someone opens a pidfd for a struct pid a pidfs dentry is allocated
and stashed in pid->stashed. Once the last pidfd for the struct pid is
closed the pidfs dentry is released and removed from pid->stashed.
So if 10 callers create a pidfs dentry for the same struct pid
sequentially, i.e., each closing the pidfd before the other creates a
new one then a new pidfs dentry is allocated every time.
Because multiple tasks acquiring and releasing a pidfd for the same
struct pid can race with each another a task may still find a valid
pidfs entry from the previous task in pid->stashed and reuse it. Or it
might find a dead dentry in there and fail to reuse it and so stashes a
new pidfs dentry. Multiple tasks may race to stash a new pidfs dentry
but only one will succeed, the other ones will put their dentry.
The current scheme aims to ensure that a pidfs dentry for a struct pid
can only be created if the task is still alive or if a pidfs dentry
already existed before the task was reaped and so exit information has
been was stashed in the pidfs inode.
That's great except that it's buggy. If a pidfs dentry is stashed in
pid->stashed after pidfs_exit() but before __unhash_process() is called
we will return a pidfd for a reaped task without exit information being
available.
The pidfds_pid_valid() check does not guard against this race as it
doens't sync at all with pidfs_exit(). The pid_has_task() check might be
successful simply because we're before __unhash_process() but after
pidfs_exit().
Introduce a new scheme where the lifetime of information associated with
a pidfs entry (coredump and exit information) isn't bound to the
lifetime of the pidfs inode but the struct pid itself.
The first time a pidfs dentry is allocated for a struct pid a struct
pidfs_attr will be allocated which will be used to store exit and
coredump information.
If all pidfs for the pidfs dentry are closed the dentry and inode can be
cleaned up but the struct pidfs_attr will stick until the struct pid
itself is freed. This will ensure minimal memory usage while persisting
relevant information.
The new scheme has various advantages. First, it allows to close the
race where we end up handing out a pidfd for a reaped task for which no
exit information is available. Second, it minimizes memory usage.
Third, it allows to remove complex lifetime tracking via dentries when
registering a struct pid with pidfs. There's no need to get or put a
reference. Instead, the lifetime of exit and coredump information
associated with a struct pid is bound to the lifetime of struct pid
itself.
Now that we have a way to persist information for pidfs dentries we can
start supporting extended attributes on pidfds. This will allow
userspace to attach meta information to tasks.
One natural extension would be to introduce a custom pidfs.* extended
attribute space and allow for the inheritance of extended attributes
across fork() and exec().
The first simple scheme will allow privileged userspace to set trusted
extended attributes on pidfs inodes.
* patches from https://lore.kernel.org/20250618-work-pidfs-persistent-v2-0-98f3456fd552@kernel.org:
pidfs: add some CONFIG_DEBUG_VFS asserts
selftests/pidfd: test setattr support
selftests/pidfd: test extended attribute support
selftests/pidfd: test extended attribute support
pidfs: support xattrs on pidfds
pidfs: make inodes mutable
libfs: prepare to allow for non-immutable pidfd inodes
pidfs: remove pidfs_pid_valid()
pidfs: remove pidfs_{get,put}_pid()
pidfs: remove custom inode allocation
pidfs: remove unused members from struct pidfs_inode
pidfs: persist information
pidfs: move to anonymous struct
libfs: massage path_from_stashed()
libfs: massage path_from_stashed() to allow custom stashing behavior
pidfs: raise SB_I_NODEV and SB_I_NOEXEC
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-0-98f3456fd552@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Allow to catch some obvious bugs.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-16-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Verify that ->setattr() on a pidfd doens't work.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-15-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Test that extended attributes are permanent.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-14-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add tests for extended attribute support on pidfds.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-13-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Now that we have a way to persist information for pidfs dentries we can
start supporting extended attributes on pidfds. This will allow
userspace to attach meta information to tasks.
One natural extension would be to introduce a custom pidfs.* extended
attribute space and allow for the inheritance of extended attributes
across fork() and exec().
The first simple scheme will allow privileged userspace to set trusted
extended attributes on pidfs inodes.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-12-98f3456fd552@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Prepare for allowing extended attributes to be set on pidfd inodes by
allowing them to be mutable.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-11-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Allow for S_IMMUTABLE to be stripped so that we can support xattrs.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-10-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The validation is now completely handled in path_from_stashed().
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-9-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Now that we stash persistent information in struct pid there's no need
to play volatile games with pinning struct pid via dentries in pidfs.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-8-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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We don't need it anymore as persistent information is allocated lazily
and stashed in struct pid.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-7-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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We've moved persistent information to struct pid.
So there's no need for these anymore.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-6-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Persist exit and coredump information independent of whether anyone
currently holds a pidfd for the struct pid.
The current scheme allocated pidfs dentries on-demand repeatedly.
This scheme is reaching it's limits as it makes it impossible to pin
information that needs to be available after the task has exited or
coredumped and that should not be lost simply because the pidfd got
closed temporarily. The next opener should still see the stashed
information.
This is also a prerequisite for supporting extended attributes on
pidfds to allow attaching meta information to them.
If someone opens a pidfd for a struct pid a pidfs dentry is allocated
and stashed in pid->stashed. Once the last pidfd for the struct pid is
closed the pidfs dentry is released and removed from pid->stashed.
So if 10 callers create a pidfs dentry for the same struct pid
sequentially, i.e., each closing the pidfd before the other creates a
new one then a new pidfs dentry is allocated every time.
Because multiple tasks acquiring and releasing a pidfd for the same
struct pid can race with each another a task may still find a valid
pidfs entry from the previous task in pid->stashed and reuse it. Or it
might find a dead dentry in there and fail to reuse it and so stashes a
new pidfs dentry. Multiple tasks may race to stash a new pidfs dentry
but only one will succeed, the other ones will put their dentry.
The current scheme aims to ensure that a pidfs dentry for a struct pid
can only be created if the task is still alive or if a pidfs dentry
already existed before the task was reaped and so exit information has
been was stashed in the pidfs inode.
That's great except that it's buggy. If a pidfs dentry is stashed in
pid->stashed after pidfs_exit() but before __unhash_process() is called
we will return a pidfd for a reaped task without exit information being
available.
The pidfds_pid_valid() check does not guard against this race as it
doens't sync at all with pidfs_exit(). The pid_has_task() check might be
successful simply because we're before __unhash_process() but after
pidfs_exit().
Introduce a new scheme where the lifetime of information associated with
a pidfs entry (coredump and exit information) isn't bound to the
lifetime of the pidfs inode but the struct pid itself.
The first time a pidfs dentry is allocated for a struct pid a struct
pidfs_attr will be allocated which will be used to store exit and
coredump information.
If all pidfs for the pidfs dentry are closed the dentry and inode can be
cleaned up but the struct pidfs_attr will stick until the struct pid
itself is freed. This will ensure minimal memory usage while persisting
relevant information.
The new scheme has various advantages. First, it allows to close the
race where we end up handing out a pidfd for a reaped task for which no
exit information is available. Second, it minimizes memory usage.
Third, it allows to remove complex lifetime tracking via dentries when
registering a struct pid with pidfs. There's no need to get or put a
reference. Instead, the lifetime of exit and coredump information
associated with a struct pid is bound to the lifetime of struct pid
itself.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-5-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Move the pidfs entries to an anonymous struct.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-4-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Make it a littler easier to follow.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-3-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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* Add a callback to struct stashed_operations so it's possible to
implement custom behavior for pidfs and allow for it to return errors.
* Teach stashed_dentry_get() to handle error pointers.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-2-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Similar to commit 1ed95281c0c7 ("anon_inode: raise SB_I_NODEV and SB_I_NOEXEC"):
it shouldn't be possible to execute pidfds via
execveat(fd_anon_inode, "", NULL, NULL, AT_EMPTY_PATH)
so raise SB_I_NOEXEC so that no one gets any creative ideas.
Also raise SB_I_NODEV as we don't expect or support any devices on pidfs.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-1-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux
Pull turbostat updates from Len Brown:
- Add initial DMR support, which required smarter RAPL probe
- Fix AMD MSR RAPL energy reporting
- Add RAPL power limit configuration output
- Minor fixes
* tag 'turbostat-2025.06.08' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux:
tools/power turbostat: version 2025.06.08
tools/power turbostat: Add initial support for BartlettLake
tools/power turbostat: Add initial support for DMR
tools/power turbostat: Dump RAPL sysfs info
tools/power turbostat: Avoid probing the same perf counters
tools/power turbostat: Allow probing RAPL with platform_features->rapl_msrs cleared
tools/power turbostat: Clean up add perf/msr counter logic
tools/power turbostat: Introduce add_msr_counter()
tools/power turbostat: Remove add_msr_perf_counter_()
tools/power turbostat: Remove add_cstate_perf_counter_()
tools/power turbostat: Remove add_rapl_perf_counter_()
tools/power turbostat: Quit early for unsupported RAPL counters
tools/power turbostat: Always check rapl_joules flag
tools/power turbostat: Fix AMD package-energy reporting
tools/power turbostat: Fix RAPL_GFX_ALL typo
tools/power turbostat: Add Android support for MSR device handling
tools/power turbostat.8: pm_domain wording fix
tools/power turbostat.8: fix typo: idle_pct should be pct_idle
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer cleanup from Thomas Gleixner:
"The delayed from_timer() API cleanup:
The renaming to the timer_*() namespace was delayed due massive
conflicts against Linux-next. Now that everything is upstream finish
the conversion"
* tag 'timers-cleanups-2025-06-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
treewide, timers: Rename from_timer() to timer_container_of()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Thomas Gleixner:
"A small set of x86 fixes:
- Cure IO bitmap inconsistencies
A failed fork cleans up all resources of the newly created thread
via exit_thread(). exit_thread() invokes io_bitmap_exit() which
does the IO bitmap cleanups, which unfortunately assume that the
cleanup is related to the current task, which is obviously bogus.
Make it work correctly
- A lockdep fix in the resctrl code removed the clearing of the
command buffer in two places, which keeps stale error messages
around. Bring them back.
- Remove unused trace events"
* tag 'x86-urgent-2025-06-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
fs/resctrl: Restore the rdt_last_cmd_clear() calls after acquiring rdtgroup_mutex
x86/iopl: Cure TIF_IO_BITMAP inconsistencies
x86/fpu: Remove unused trace events
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Thomas Gleixner:
"Add the missing seq_file forward declaration in the timer namespace
header"
* tag 'timers-urgent-2025-06-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timens: Add struct seq_file forward declaration
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Add initial DMR support, which required smarter RAPL probe
Fix AMD MSR RAPL energy reporting
Add RAPL power limit configuration output
Minor fixes
Signed-off-by: Len Brown <len.brown@intel.com>
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Add initial support for BartlettLake.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
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Add initial support for DMR.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
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for example:
intel-rapl:1: psys 28.0s:100W 976.0us:100W
intel-rapl:0: package-0 28.0s:57W,max:15W 2.4ms:57W
intel-rapl:0/intel-rapl:0:0: core disabled
intel-rapl:0/intel-rapl:0:1: uncore disabled
intel-rapl-mmio:0: package-0 28.0s:28W,max:15W 2.4ms:57W
[lenb: simplified format]
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
squish me
Signed-off-by: Len Brown <len.brown@intel.com>
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For the RAPL package energy status counter, Intel and AMD share the same
perf_subsys and perf_name, but with different MSR addresses.
Both rapl_counter_arch_infos[0] and rapl_counter_arch_infos[1] are
introduced to describe this counter for different Vendors.
As a result, the perf counter is probed twice, and causes a failure in
in get_rapl_counters() because expected_read_size and actual_read_size
don't match.
Fix the problem by skipping the already probed counter.
Note, this is not a perfect fix. For example, if different
vendors/platforms use the same MSR value for different purpose, the code
can be fooled when it probes a rapl_counter_arch_infos[] entry that does
not belong to the running Vendor/Platform.
In a long run, better to put rapl_counter_arch_infos[] into the
platform_features so that this becomes Vendor/Platform specific.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
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