5.4-stable patches

added patches:
	filelock-remove-locks-reliably-when-fcntl-close-race-is-detected.patch

diff --git a/queue-5.4/filelock-remove-locks-reliably-when-fcntl-close-race-is-detected.patch b/queue-5.4/filelock-remove-locks-reliably-when-fcntl-close-race-is-detected.patch
new file mode 100644 (file)
index 0000000..a33202b
--- /dev/null
+++ b/queue-5.4/filelock-remove-locks-reliably-when-fcntl-close-race-is-detected.patch
@@ -0,0 +1,66 @@
+From 3cad1bc010416c6dd780643476bc59ed742436b9 Mon Sep 17 00:00:00 2001
+From: Jann Horn <jannh@google.com>
+Date: Tue, 2 Jul 2024 18:26:52 +0200
+Subject: filelock: Remove locks reliably when fcntl/close race is detected
+
+From: Jann Horn <jannh@google.com>
+
+commit 3cad1bc010416c6dd780643476bc59ed742436b9 upstream.
+
+When fcntl_setlk() races with close(), it removes the created lock with
+do_lock_file_wait().
+However, LSMs can allow the first do_lock_file_wait() that created the lock
+while denying the second do_lock_file_wait() that tries to remove the lock.
+In theory (but AFAIK not in practice), posix_lock_file() could also fail to
+remove a lock due to GFP_KERNEL allocation failure (when splitting a range
+in the middle).
+
+After the bug has been triggered, use-after-free reads will occur in
+lock_get_status() when userspace reads /proc/locks. This can likely be used
+to read arbitrary kernel memory, but can't corrupt kernel memory.
+This only affects systems with SELinux / Smack / AppArmor / BPF-LSM in
+enforcing mode and only works from some security contexts.
+
+Fix it by calling locks_remove_posix() instead, which is designed to
+reliably get rid of POSIX locks associated with the given file and
+files_struct and is also used by filp_flush().
+
+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/20240702-fs-lock-recover-2-v1-1-edd456f63789@google.com
+Reviewed-by: Jeff Layton <jlayton@kernel.org>
+Signed-off-by: Christian Brauner <brauner@kernel.org>
+[stable fixup: ->c.flc_type was ->fl_type in older kernels]
+Signed-off-by: Jann Horn <jannh@google.com>
+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
+@@ -2526,8 +2526,9 @@ int fcntl_setlk(unsigned int fd, struct
+       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 &&
+@@ -2541,9 +2542,7 @@ int fcntl_setlk(unsigned int fd, struct
+               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, files);
+                       error = -EBADF;
+               }
+       }

diff --git a/queue-5.4/series b/queue-5.4/series
index 0c400691d60c353ed160d543b54b026a8e777ec4..17637ed2a375a80353428077e308da9217b6c354 100644 (file)
--- a/queue-5.4/series
+++ b/queue-5.4/series
@@ -1 +1,2 @@
 gcc-plugins-rename-last_stmt-for-gcc-14.patch
+filelock-remove-locks-reliably-when-fcntl-close-race-is-detected.patch