commit ccbfcac05866ebe6eb3bc6d07b51d4ed4fcde436 upstream.
The recent addition of a sanity check for a too low start tick time
seems breaking some applications that uses aloop with a certain slave
timer setup. They may have the initial resolution 0, hence it's
treated as if it were a too low value.
Relax and skip the check for the slave timer instance for addressing
the regression.
Fixes: 4a63bd179fa8 ("ALSA: timer: Set lower bound of start tick time")
Cc: <stable@vger.kernel.org>
Link: https://github.com/raspberrypi/linux/issues/6294
Link: https://patch.msgid.link/20240810084833.10939-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
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>
[ backport note: the error handling is changed, as the original commit
is based on the recent cleanup with guard() in commit beb45974dd49
-- tiwai ]
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
