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Commit e308b103 authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Greg Kroah-Hartman
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ALSA: seq: oss: Fix Spectre v1 vulnerability 

commit c709f14f0616482b67f9fbcb965e1493a03ff30b upstream.

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: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c84a7647

sound/core/seq/oss/seq_oss_synth.c

+4 −3
Original line number Diff line number Diff line
@@ -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;