BACKPORT: ALSA: seq: Make ioctls race-free
commit b3defb791b26ea0683a93a4f49c77ec45ec96f10 upstream.
The ALSA sequencer ioctls have no protection against racy calls while
the concurrent operations may lead to interfere with each other. As
reported recently, for example, the concurrent calls of setting client
pool with a combination of write calls may lead to either the
unkillable dead-lock or UAF.
As a slightly big hammer solution, this patch introduces the mutex to
make each ioctl exclusive. Although this may reduce performance via
parallel ioctl calls, usually it's not demanded for sequencer usages,
hence it should be negligible.
BUG=chromium:808786
TEST=Build and run
Change-Id: Iee3322cb46ff9b8850ffa003912b6ff67da5e14c
Reported-by: Luo Quan <a4651386@163.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 4.4: ioctl dispatch is done from snd_seq_do_ioctl();
take the mutex and add ret variable there.]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[backport: see 4.4 comments above]
Signed-off-by: Guenter Roeck <groeck@chromium.org>
(cherry picked from commit 623e5c8ae32b39cc8baea83478695dc624935318)
Reviewed-on: https://chromium-review.googlesource.com/900831
2 files changed
