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authorDavid Howells <dhowells@redhat.com>2019-12-05 22:30:30 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2019-12-05 15:33:50 -0800
commit8c7b8c34ae952cc062c12d7db9ee2f298c09dca4 (patch)
tree2b51d3882e2b1a9126e37725a6e1525f5a763e00 /fs/pipe.c
parent3c0edea9b29f9be6c093f236f762202b30ac9431 (diff)
pipe: Remove assertion from pipe_poll()
An assertion check was added to pipe_poll() to make sure that the ring occupancy isn't seen to overflow the ring size. However, since no locks are held when the three values are read, it is possible for F_SETPIPE_SZ to intervene and muck up the calculation, thereby causing the oops. Fix this by simply removing the assertion and accepting that the calculation might be approximate. Note that the previous code also had a similar issue, though there was no assertion check, since the occupancy counter and the ring size were not read with a lock held, so it's possible that the poll check might have malfunctioned then too. Also wake up all the waiters so that they can reissue their checks if there was a competing read or write. Fixes: 8cefc107ca54 ("pipe: Use head and tail pointers for the ring, not cursor and length") Reported-by: syzbot+d37abaade33a934f16f2@syzkaller.appspotmail.com Signed-off-by: David Howells <dhowells@redhat.com> cc: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/pipe.c')
-rw-r--r--fs/pipe.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index c5e3765465f0..05330fac081f 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -579,8 +579,6 @@ pipe_poll(struct file *filp, poll_table *wait)
poll_wait(filp, &pipe->wait, wait);
- BUG_ON(pipe_occupancy(head, tail) > pipe->ring_size);
-
/* Reading only -- no need for acquiring the semaphore. */
mask = 0;
if (filp->f_mode & FMODE_READ) {
@@ -1174,6 +1172,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
pipe->max_usage = nr_slots;
pipe->tail = tail;
pipe->head = head;
+ wake_up_interruptible_all(&pipe->wait);
return pipe->max_usage * PAGE_SIZE;
out_revert_acct: