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authorSteven Rostedt (Google) <rostedt@goodmis.org>2022-10-26 23:12:36 -0400
committerTakashi Iwai <tiwai@suse.de>2022-10-27 08:42:08 +0200
commitf0a868788fcbf63cdab51f5adcf73b271ede8164 (patch)
tree49269e38809f1953cb26942cf5cb77c7207d0e4a
parent4a4c8482e370d697738a78dcd7bf2780832cb712 (diff)
ALSA: Use del_timer_sync() before freeing timer
The current code for freeing the emux timer is extremely dangerous: CPU0 CPU1 ---- ---- snd_emux_timer_callback() snd_emux_free() spin_lock(&emu->voice_lock) del_timer(&emu->tlist); <-- returns immediately spin_unlock(&emu->voice_lock); [..] kfree(emu); spin_lock(&emu->voice_lock); [BOOM!] Instead just use del_timer_sync() which will wait for the timer to finish before continuing. No need to check if the timer is active or not when doing so. This doesn't fix the race of a possible re-arming of the timer, but at least it won't use the data that has just been freed. [ Fixed unused variable warning by tiwai ] Cc: stable@vger.kernel.org Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/20221026231236.6834b551@gandalf.local.home Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/synth/emux/emux.c7
1 files changed, 1 insertions, 6 deletions
diff --git a/sound/synth/emux/emux.c b/sound/synth/emux/emux.c
index 5ed8e36d2e04..a870759d179e 100644
--- a/sound/synth/emux/emux.c
+++ b/sound/synth/emux/emux.c
@@ -126,15 +126,10 @@ EXPORT_SYMBOL(snd_emux_register);
*/
int snd_emux_free(struct snd_emux *emu)
{
- unsigned long flags;
-
if (! emu)
return -EINVAL;
- spin_lock_irqsave(&emu->voice_lock, flags);
- if (emu->timer_active)
- del_timer(&emu->tlist);
- spin_unlock_irqrestore(&emu->voice_lock, flags);
+ del_timer_sync(&emu->tlist);
snd_emux_proc_free(emu);
snd_emux_delete_virmidi(emu);