]> git.ipfire.org Git - thirdparty/kernel/stable.git/commitdiff
ALSA: rawmidi: Fix potential Spectre v1 vulnerability
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Wed, 20 Mar 2019 21:15:24 +0000 (16:15 -0500)
committerBen Hutchings <ben@decadent.org.uk>
Tue, 13 Aug 2019 11:38:50 +0000 (12:38 +0100)
commit 2b1d9c8f87235f593826b9cf46ec10247741fff9 upstream.

info->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/rawmidi.c:604 __snd_rawmidi_info_select() warn: potential spectre issue 'rmidi->streams' [r] (local cap)

Fix this by sanitizing info->stream before using it to index
rmidi->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://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
sound/core/rawmidi.c

index 2bd5b85241817ff7108cbb2925f950317346adbf..09e05c0b59a1c46494f47acb6df7ba7d11bf2507 100644 (file)
@@ -29,6 +29,7 @@
 #include <linux/mutex.h>
 #include <linux/module.h>
 #include <linux/delay.h>
+#include <linux/nospec.h>
 #include <sound/rawmidi.h>
 #include <sound/info.h>
 #include <sound/control.h>
@@ -601,6 +602,7 @@ static int __snd_rawmidi_info_select(struct snd_card *card,
                return -ENXIO;
        if (info->stream < 0 || info->stream > 1)
                return -EINVAL;
+       info->stream = array_index_nospec(info->stream, 2);
        pstr = &rmidi->streams[info->stream];
        if (pstr->substream_count == 0)
                return -ENOENT;