4.20-stable review patch. If anyone has any objections, please let me know.
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From: Gustavo A. R. Silva gustavo@embeddedor.com
commit 94ffb030b6d31ec840bb811be455dd2e26a4f43e upstream.
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
Signed-off-by: Gustavo A. R. Silva gustavo@embeddedor.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- sound/core/pcm.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -25,6 +25,7 @@ #include <linux/time.h> #include <linux/mutex.h> #include <linux/device.h> +#include <linux/nospec.h> #include <sound/core.h> #include <sound/minors.h> #include <sound/pcm.h> @@ -129,6 +130,7 @@ static int snd_pcm_control_ioctl(struct 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(®ister_mutex);