5.10-stable review patch. If anyone has any objections, please let me know.
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From: Eric Sandeen sandeen@redhat.com
[ Upstream commit f13abc1e8e1a3b7455511c4e122750127f6bc9b0 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/watch_queue.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index 73717917d8164..37da8647b4ecb 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -274,6 +274,15 @@ 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(sizeof(struct page *), nr_pages, GFP_KERNEL); if (!pages)