From 932c29a10d5d0bba63b9f505a8ec1e3ce8c02542 Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 17 Aug 2022 19:41:27 +0100 Subject: locks: Fix dropped call to ->fl_release_private() Prior to commit 4149be7bda7e, sys_flock() would allocate the file_lock struct it was going to use to pass parameters, call ->flock() and then call locks_free_lock() to get rid of it - which had the side effect of calling locks_release_private() and thus ->fl_release_private(). With commit 4149be7bda7e, however, this is no longer the case: the struct is now allocated on the stack, and locks_free_lock() is no longer called - and thus any remaining private data doesn't get cleaned up either. This causes afs flock to cause oops. Kasan catches this as a UAF by the list_del_init() in afs_fl_release_private() for the file_lock record produced by afs_fl_copy_lock() as the original record didn't get delisted. It can be reproduced using the generic/504 xfstest. Fix this by reinstating the locks_release_private() call in sys_flock(). I'm not sure if this would affect any other filesystems. If not, then the release could be done in afs_flock() instead. Changes ======= ver #2) - Don't need to call ->fl_release_private() after calling the security hook, only after calling ->flock(). Fixes: 4149be7bda7e ("fs/lock: Don't allocate file_lock in flock_make_lock().") cc: Chuck Lever cc: Jeff Layton cc: Marc Dionne cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/166075758809.3532462.13307935588777587536.stgit@warthog.procyon.org.uk/ # v1 Acked-by: Kuniyuki Iwashima Signed-off-by: David Howells Signed-off-by: Jeff Layton --- fs/locks.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/locks.c') diff --git a/fs/locks.c b/fs/locks.c index c266cfdc3291..607f94a0e789 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -2129,6 +2129,7 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) else error = locks_lock_file_wait(f.file, &fl); + locks_release_private(&fl); out_putf: fdput(f); -- cgit v1.2.3