From: Takashi Iwai Date: Tue, 23 Aug 2022 07:27:16 +0000 (+0200) Subject: ALSA: seq: oss: Fix data-race for max_midi_devs access X-Git-Tag: v5.15.73~464 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9b7a07fcc5d4918c4722a3522a14092efc8ed090;p=platform%2Fkernel%2Flinux-rpi.git ALSA: seq: oss: Fix data-race for max_midi_devs access commit 22dec134dbfa825b963f8a1807ad19b943e46a56 upstream. ALSA OSS sequencer refers to a global variable max_midi_devs at creating a new port, storing it to its own field. Meanwhile this variable may be changed by other sequencer events at snd_seq_oss_midi_check_exit_port() in parallel, which may cause a data race. OTOH, this data race itself is almost harmless, as the access to the MIDI device is done via get_mdev() and it's protected with a refcount, hence its presence is guaranteed. Though, it's sill better to address the data-race from the code sanity POV, and this patch adds the proper spinlock for the protection. Reported-by: Abhishek Shah Cc: Link: https://lore.kernel.org/r/CAEHB2493pZRXs863w58QWnUTtv3HHfg85aYhLn5HJHCwxqtHQg@mail.gmail.com Link: https://lore.kernel.org/r/20220823072717.1706-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- diff --git a/sound/core/seq/oss/seq_oss_midi.c b/sound/core/seq/oss/seq_oss_midi.c index 1e3bf08..07efb38 100644 --- a/sound/core/seq/oss/seq_oss_midi.c +++ b/sound/core/seq/oss/seq_oss_midi.c @@ -270,7 +270,9 @@ snd_seq_oss_midi_clear_all(void) void snd_seq_oss_midi_setup(struct seq_oss_devinfo *dp) { + spin_lock_irq(®ister_lock); dp->max_mididev = max_midi_devs; + spin_unlock_irq(®ister_lock); } /*