filelock: Fix fcntl/close race recovery compat path

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>

diff --git a/fs/locks.c b/fs/locks.c
index 7957a5aa84967eabe1b408bdcc57d5b2553077b5..234ebfa8c0701c1dc0f1d1c90c7c51abb37a5aa3 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -2427,8 +2427,9 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
        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 &&
@@ -2442,9 +2443,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
                f = fcheck(fd);
                spin_unlock(&current->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, &current->files);
                        error = -EBADF;
                }
        }