ALSA: seq: Fix missing NULL check at remove_events ioctl

Orabug: 23330522

commit 030e2c78d3a91dd0d27fef37e91950dde333eba1 upstream.

snd_seq_ioctl_remove_events() calls snd_seq_fifo_clear()
unconditionally even if there is no FIFO assigned, and this leads to
an Oops due to NULL dereference.  The fix is just to add a proper NULL
check.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 9a6003a362acb814fea7422209be344b822b047a)

Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index edbdab85fc02f6f8a54388e9f1b353559661497e..bd4741442909a020a21bf55807bcf7b5dad1335e 100644 (file)
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1962,7 +1962,7 @@ static int snd_seq_ioctl_remove_events(struct snd_seq_client *client,
                 * No restrictions so for a user client we can clear
                 * the whole fifo
                 */
-               if (client->type == USER_CLIENT)
+               if (client->type == USER_CLIENT && client->data.user.fifo)
                        snd_seq_fifo_clear(client->data.user.fifo);
        }