* [PATCH] ALSA: seq: oss: Fix Spectre v1 vulnerability
@ 2019-03-20 23:42 Gustavo A. R. Silva
2019-03-21 12:25 ` Takashi Iwai
0 siblings, 1 reply; 2+ messages in thread
From: Gustavo A. R. Silva @ 2019-03-20 23:42 UTC (permalink / raw)
To: Jaroslav Kysela, Takashi Iwai
Cc: alsa-devel, linux-kernel, Gustavo A. R. Silva
dev 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/seq/oss/seq_oss_synth.c:626 snd_seq_oss_synth_make_info() warn: potential spectre issue 'dp->synths' [w] (local cap)
Fix this by sanitizing dev before using it to index dp->synths.
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/
Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
sound/core/seq/oss/seq_oss_synth.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/sound/core/seq/oss/seq_oss_synth.c b/sound/core/seq/oss/seq_oss_synth.c
index 278ebb993122..c93945917235 100644
--- a/sound/core/seq/oss/seq_oss_synth.c
+++ b/sound/core/seq/oss/seq_oss_synth.c
@@ -617,13 +617,14 @@ int
snd_seq_oss_synth_make_info(struct seq_oss_devinfo *dp, int dev, struct synth_info *inf)
{
struct seq_oss_synth *rec;
+ struct seq_oss_synthinfo *info = get_synthinfo_nospec(dp, dev);
- if (dev < 0 || dev >= dp->max_synthdev)
+ if (!info)
return -ENXIO;
- if (dp->synths[dev].is_midi) {
+ if (info->is_midi) {
struct midi_info minf;
- snd_seq_oss_midi_make_info(dp, dp->synths[dev].midi_mapped, &minf);
+ snd_seq_oss_midi_make_info(dp, info->midi_mapped, &minf);
inf->synth_type = SYNTH_TYPE_MIDI;
inf->synth_subtype = 0;
inf->nr_voices = 16;
--
2.21.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] ALSA: seq: oss: Fix Spectre v1 vulnerability
2019-03-20 23:42 [PATCH] ALSA: seq: oss: Fix Spectre v1 vulnerability Gustavo A. R. Silva
@ 2019-03-21 12:25 ` Takashi Iwai
0 siblings, 0 replies; 2+ messages in thread
From: Takashi Iwai @ 2019-03-21 12:25 UTC (permalink / raw)
To: Gustavo A. R. Silva ; +Cc: Jaroslav Kysela, alsa-devel, linux-kernel
On Thu, 21 Mar 2019 00:42:01 +0100,
Gustavo A. R. Silva wrote:
>
> dev 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/seq/oss/seq_oss_synth.c:626 snd_seq_oss_synth_make_info() warn: potential spectre issue 'dp->synths' [w] (local cap)
>
> Fix this by sanitizing dev before using it to index dp->synths.
>
> 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/
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Applied, thanks.
Takashi
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