From 9fdc9668fa45623b320abfab0ec1508b4275425d Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Mon, 13 Jun 2022 08:27:18 +0000 Subject: [PATCH] ALSA: pcm: Fix races among concurrent read/write and buffer changes stable inclusion from linux-4.19.243 commit b3830197aa7413c65767cf5a1aa8775c83f0dbf7 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I50WAS CVE: CVE-2022-1048 -------------------------------- commit dca947d4d26dbf925a64a6cfb2ddbc035e831a3d upstream. In the current PCM design, the read/write syscalls (as well as the equivalent ioctls) are allowed before the PCM stream is running, that is, at PCM PREPARED state. Meanwhile, we also allow to re-issue hw_params and hw_free ioctl calls at the PREPARED state that may change or free the buffers, too. The problem is that there is no protection against those mix-ups. This patch applies the previously introduced runtime->buffer_mutex to the read/write operations so that the concurrent hw_params or hw_free call can no longer interfere during the operation. The mutex is unlocked before scheduling, so we don't take it too long. Cc: Reviewed-by: Jaroslav Kysela Link: https://lore.kernel.org/r/20220322170720.3529-3-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Ovidiu Panait Signed-off-by: Greg Kroah-Hartman Signed-off-by: Rui Xiang Reviewed-by: zhangxiaoxu Reviewed-by: Xiu Jianfeng Signed-off-by: Yongqiang Liu --- sound/core/pcm_lib.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index ad52126d3d22..3e95e0f5968b 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1875,9 +1875,11 @@ static int wait_for_avail(struct snd_pcm_substream *substream, if (avail >= runtime->twake) break; snd_pcm_stream_unlock_irq(substream); + mutex_unlock(&runtime->buffer_mutex); tout = schedule_timeout(wait_time); + mutex_lock(&runtime->buffer_mutex); snd_pcm_stream_lock_irq(substream); set_current_state(TASK_INTERRUPTIBLE); switch (runtime->status->state) { @@ -2171,6 +2173,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, nonblock = !!(substream->f_flags & O_NONBLOCK); + mutex_lock(&runtime->buffer_mutex); snd_pcm_stream_lock_irq(substream); err = pcm_accessible_state(runtime); if (err < 0) @@ -2253,6 +2256,7 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, if (xfer > 0 && err >= 0) snd_pcm_update_state(substream, runtime); snd_pcm_stream_unlock_irq(substream); + mutex_unlock(&runtime->buffer_mutex); return xfer > 0 ? (snd_pcm_sframes_t)xfer : err; } EXPORT_SYMBOL(__snd_pcm_lib_xfer); -- GitLab