On Thu, 21 Jan 2021 17:30:40 +0300 Denis Efremov efremov@linux.com wrote:
Hi,
This patch (CVE-2020-27825) was tagged with Fixes: b23d7a5f4a07a ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU")
I'm not an expert here but it seems like b23d7a5f4a07a only refactored ring_buffer_reset_cpu() by introducing reset_disabled_cpu_buffer() without significant changes. Hence, mutex_lock(&buffer->mutex)/mutex_unlock(&buffer->mutex) can be backported further than b23d7a5f4a07a~ and to all LTS kernels. Is b23d7a5f4a07a the actual cause of the bug?
Ug, that looks to be a mistake. Looking back at the thread about this:
https://lore.kernel.org/linux-arm-msm/20200915141304.41fa7c30@gandalf.local....
That should have been:
Depends-on: b23d7a5f4a07 ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU")
-- Steve