diff options
| author | Eric Sandeen <sandeen@redhat.com> | 2025-02-27 11:41:08 -0600 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-03-01 11:02:35 +0100 |
| commit | f13abc1e8e1a3b7455511c4e122750127f6bc9b0 (patch) | |
| tree | 66e795bbc8f75e76111228f9dbeb5930353bb668 | |
| parent | e249056c91a2f14ee40de2bf24cf72d8e68101f5 (diff) | |
watch_queue: fix pipe accounting mismatch
Currently, watch_queue_set_size() modifies the pipe buffers charged to
user->pipe_bufs without updating the pipe->nr_accounted on the pipe
itself, due to the if (!pipe_has_watch_queue()) test in
pipe_resize_ring(). This means that when the pipe is ultimately freed,
we decrement user->pipe_bufs by something other than what than we had
charged to it, potentially leading to an underflow. This in turn can
cause subsequent too_many_pipe_buffers_soft() tests to fail with -EPERM.
To remedy this, explicitly account for the pipe usage in
watch_queue_set_size() to match the number set via account_pipe_buffers()
(It's unclear why watch_queue_set_size() does not update nr_accounted;
it may be due to intentional overprovisioning in watch_queue_set_size()?)
Fixes: e95aada4cb93d ("pipe: wakeup wr_wait after setting max_usage")
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Link: https://lore.kernel.org/r/206682a8-0604-49e5-8224-fdbe0c12b460@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | kernel/watch_queue.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index 5267adeaa403..41e4e8070923 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -269,6 +269,15 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes) if (ret < 0) goto error; + /* + * pipe_resize_ring() does not update nr_accounted for watch_queue + * pipes, because the above vastly overprovisions. Set nr_accounted on + * and max_usage this pipe to the number that was actually charged to + * the user above via account_pipe_buffers. + */ + pipe->max_usage = nr_pages; + pipe->nr_accounted = nr_pages; + ret = -ENOMEM; pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL); if (!pages) |