stream is indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

sound/core/pcm.c:140 snd_pcm_control_ioctl() warn: potential spectre issue 'pcm->streams' [r] (local cap)

Fix this by sanitizing stream before using it to index pcm->streams

Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2

Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com --- sound/core/pcm.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/sound/core/pcm.c b/sound/core/pcm.c index fdb9b92fc8d6..23141003a90d 100644 --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -32,6 +32,8 @@ #include <sound/control.h> #include <sound/info.h>

+#include <linux/nospec.h> + #include "pcm_local.h"

MODULE_AUTHOR("Jaroslav Kysela perex@perex.cz, Abramo Bagnara abramo@alsa-project.org"); @@ -129,6 +131,7 @@ static int snd_pcm_control_ioctl(struct snd_card *card, return -EFAULT; if (stream < 0 || stream > 1) return -EINVAL; + stream = array_index_nospec(stream, 2); if (get_user(subdevice, &info->subdevice)) return -EFAULT; mutex_lock(&register_mutex);