[PATCH 6.6 16/16] filelock: Fix fcntl/close race recovery compat path

Greg Kroah-Hartman
2024-07-25T14:45:27Z

From: Jann Horn <jannh@google.com>

commit f8138f2ad2f745b9a1c696a05b749eabe44337ea upstream.

When I wrote commit 3cad1bc01041 ("filelock: Remove locks reliably when
fcntl/close race is detected"), I missed that there are two copies of the
code I was patching: The normal version, and the version for 64-bit offsets
on 32-bit kernels.
Thanks to Greg KH for stumbling over this while doing the stable
backport...

Apply exactly the same fix to the compat path for 32-bit kernels.

Fixes: c293621bbf67 ("[PATCH] stale POSIX lock handling")
Cc: stable@kernel.org
Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2563
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20240723-fs-lock-recover-compatfix-v1-1-148096719529@google.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/locks.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2503,8 +2503,9 @@ int fcntl_setlk64(unsigned int fd, struc
error = do_lock_file_wait(filp, cmd, file_lock);

/*
- * Attempt to detect a close/fcntl race and recover by releasing the
- * lock that was just acquired. There is no need to do that when we're
+ * Detect close/fcntl races and recover by zapping all POSIX locks
+ * associated with this file and our files_struct, just like on
+ * filp_flush(). There is no need to do that when we're
* unlocking though, or for OFD locks.
*/
if (!error && file_lock->fl_type != F_UNLCK &&
@@ -2519,9 +2520,7 @@ int fcntl_setlk64(unsigned int fd, struc
f = files_lookup_fd_locked(files, fd);
spin_unlock(&files->file_lock);
if (f != filp) {
- file_lock->fl_type = F_UNLCK;
- error = do_lock_file_wait(filp, cmd, file_lock);
- WARN_ON_ONCE(error);
+ locks_remove_posix(filp, files);
error = -EBADF;
}
}