On Mon, May 27, 2024 at 08:23:59AM +0200, Takashi Iwai wrote:
commit 4a63bd179fa8d3fcc44a0d9d71d941ddd62f0c4e upstream.
Currently ALSA timer doesn't have the lower limit of the start tick time, and it allows a very small size, e.g. 1 tick with 1ns resolution for hrtimer. Such a situation may lead to an unexpected RCU stall, where the callback repeatedly queuing the expire update, as reported by fuzzer.
This patch introduces a sanity check of the timer start tick time, so that the system returns an error when a too small start size is set. As of this patch, the lower limit is hard-coded to 100us, which is small enough but can still work somehow.
[ backport note: the error handling is changed, as the original commit is based on the recent cleanup with guard() in commit beb45974dd49 -- tiwai ]
Reported-by: syzbot+43120c2af6ca2938cc38@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/000000000000fa00a1061740ab6d@google.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240514182745.4015-1-tiwai@suse.de Signed-off-by: Takashi Iwai tiwai@suse.de
Greg, this is an alternative fix to the original cherry-pick; apply to 6.8.y and older stable kernels. Thanks!
Now queued up, thanks!
greg k-h