CVE-2023-52672 — pipe: wakeup wr_wait after setting max_usage

Affected: Linux, linux_kernel

In the Linux kernel, the following vulnerability has been resolved:

pipe: wakeup wr_wait after setting max_usage

Commit c73be61cede5 ("pipe: Add general notification queue support") a regression was introduced that would lock up resized pipes under certain conditions. See the reproducer in [1].

The commit resizing the pipe ring size was moved to a different function, doing that moved the wakeup for pipe->wr_wait before actually raising pipe->max_usage. If a pipe was full before the resize occured it would result in the wakeup never actually triggering pipe_write.

Set @max_usage and @nr_accounted before waking writers if this isn't a watch queue.

[Christian Brauner <brauner@kernel.org>: rewrite to account for watch queues]

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CVE-2023-52672 — pipe: wakeup wr_wait after setting max_usage