From 566d136289dc57816ac290de87a9a0f7d9bd3cbb Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Wed, 20 May 2020 08:51:59 +0900 Subject: [PATCH] pipe: Fix pipe_full() test in opipe_prep(). syzbot is reporting that splice()ing from non-empty read side to already-full write side causes unkillable task, for opipe_prep() is by error not inverting pipe_full() test. CPU: 0 PID: 9460 Comm: syz-executor.5 Not tainted 5.6.0-rc3-next-20200228-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:rol32 include/linux/bitops.h:105 [inline] RIP: 0010:iterate_chain_key kernel/locking/lockdep.c:369 [inline] RIP: 0010:__lock_acquire+0x6a3/0x5270 kernel/locking/lockdep.c:4178 Call Trace: lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4720 __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1103 pipe_lock_nested fs/pipe.c:66 [inline] pipe_double_lock+0x1a0/0x1e0 fs/pipe.c:104 splice_pipe_to_pipe fs/splice.c:1562 [inline] do_splice+0x35f/0x1520 fs/splice.c:1141 __do_sys_splice fs/splice.c:1447 [inline] __se_sys_splice fs/splice.c:1427 [inline] __x64_sys_splice+0x2b5/0x320 fs/splice.c:1427 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xbe Reported-by: syzbot+b48daca8639150bc5e73@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=9386d051e11e09973d5a4cf79af5e8cedf79386d Fixes: 8cefc107ca54c8b0 ("pipe: Use head and tail pointers for the ring, not cursor and length") Cc: stable@vger.kernel.org # 5.5+ Signed-off-by: Tetsuo Handa Signed-off-by: Linus Torvalds --- fs/splice.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/splice.c b/fs/splice.c index fd0a1e7e5959..4e53efbd621d 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1494,7 +1494,7 @@ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags) * Check pipe occupancy without the inode lock first. This function * is speculative anyways, so missing one is ok. */ - if (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) + if (!pipe_full(pipe->head, pipe->tail, pipe->max_usage)) return 0; ret = 0;