ALSA: seq/oss - Fix double-free at error path of snd_seq_oss_open()

The error handling in snd_seq_oss_open() has several bad codes that
do dereferecing released pointers and double-free of kmalloc'ed data.
The object dp is release in free_devinfo() that is called via
private_free callback.  The rest shouldn't touch this object any more.

The patch changes delete_port() to call kfree() in any case, and gets
rid of unnecessary calls of destructors in snd_seq_oss_open().

Fixes CVE-2010-3080.

Reported-and-tested-by: Tavis Ormandy <taviso@cmpxchg8b.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/core/seq/oss/seq_oss_init.c b/sound/core/seq/oss/seq_oss_init.c
index 685712276ac95ab0d57985489b86f4f840bcf9b1..69cd7b3c362d19f4b0ac989b8bc107e49e59ff1b 100644 (file)
--- a/sound/core/seq/oss/seq_oss_init.c
+++ b/sound/core/seq/oss/seq_oss_init.c
@@ -281,13 +281,10 @@ snd_seq_oss_open(struct file *file, int level)
        return 0;
 
  _error:
-       snd_seq_oss_writeq_delete(dp->writeq);
-       snd_seq_oss_readq_delete(dp->readq);
        snd_seq_oss_synth_cleanup(dp);
        snd_seq_oss_midi_cleanup(dp);
-       delete_port(dp);
        delete_seq_queue(dp->queue);
-       kfree(dp);
+       delete_port(dp);
 
        return rc;
 }
@@ -350,8 +347,10 @@ create_port(struct seq_oss_devinfo *dp)
 static int
 delete_port(struct seq_oss_devinfo *dp)
 {
-       if (dp->port < 0)
+       if (dp->port < 0) {
+               kfree(dp);
                return 0;
+       }
 
        debug_printk(("delete_port %i\n", dp->port));
        return snd_seq_event_port_detach(dp->cseq, dp->port);