The "dev" variable could be out of bounds. Calling
snd_seq_oss_synth_is_valid() checks that it is is a valid device
which has been opened. We check this inside set_note_event() so
this function can't succeed without a valid "dev". But we need to
do the check earlier to prevent invalid dereferences and memory
corruption.
One call tree where "dev" could be out of bounds is:
-> snd_seq_oss_oob_user()
-> snd_seq_oss_process_event()
-> extended_event()
-> note_on_event()
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
diff --git a/sound/core/seq/oss/seq_oss_event.c b/sound/core/seq/oss/seq_oss_event.c
index 066f5f3..c390886 100644
--- a/sound/core/seq/oss/seq_oss_event.c
+++ b/sound/core/seq/oss/seq_oss_event.c
@@ -285,7 +285,12 @@ local_event(struct seq_oss_devinfo *dp, union evrec *q, struct snd_seq_event *ev
static int
note_on_event(struct seq_oss_devinfo *dp, int dev, int ch, int note, int vel, struct snd_seq_event *ev)
{
- struct seq_oss_synthinfo *info = &dp->synths[dev];
+ struct seq_oss_synthinfo *info;
+
+ if (!snd_seq_oss_synth_is_valid(dp, dev))
+ return -ENXIO;
+
+ info = &dp->synths[dev];
switch (info->arg.event_passing) {
case SNDRV_SEQ_OSS_PROCESS_EVENTS:
if (! info->ch || ch < 0 || ch >= info->nr_voices) {
@@ -340,7 +345,12 @@ note_on_event(struct seq_oss_devinfo *dp, int dev, int ch, int note, int vel, st
static int
note_off_event(struct seq_oss_devinfo *dp, int dev, int ch, int note, int vel, struct snd_seq_event *ev)
{
- struct seq_oss_synthinfo *info = &dp->synths[dev];
+ struct seq_oss_synthinfo *info;
+
+ if (!snd_seq_oss_synth_is_valid(dp, dev))
+ return -ENXIO;
+
+ info = &dp->synths[dev];
switch (info->arg.event_passing) {
case SNDRV_SEQ_OSS_PROCESS_EVENTS:
if (! info->ch || ch < 0 || ch >= info->nr_voices) {
--
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