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authorTakashi Iwai <tiwai@suse.de>2017-10-09 10:02:56 +0200
committerTakashi Iwai <tiwai@suse.de>2017-10-09 14:10:13 +0200
commit5803b023881857db32ffefa0d269c90280a67ee0 (patch)
treedc218d1ac325d6290ec3ca495eaa86aaa4ea461b /include/sound/seq_virmidi.h
parentc247487c0dd6fefff6ed0cbcbe66f037721755fb (diff)
ALSA: seq: Fix copy_from_user() call inside lock
The event handler in the virmidi sequencer code takes a read-lock for the linked list traverse, while it's calling snd_seq_dump_var_event() in the loop. The latter function may expand the user-space data depending on the event type. It eventually invokes copy_from_user(), which might be a potential dead-lock. The sequencer core guarantees that the user-space data is passed only with atomic=0 argument, but snd_virmidi_dev_receive_event() ignores it and always takes read-lock(). For avoiding the problem above, this patch introduces rwsem for non-atomic case, while keeping rwlock for atomic case. Also while we're at it: the superfluous irq flags is dropped in snd_virmidi_input_open(). Reported-by: Jia-Ju Bai <baijiaju1990@163.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'include/sound/seq_virmidi.h')
-rw-r--r--include/sound/seq_virmidi.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/sound/seq_virmidi.h b/include/sound/seq_virmidi.h
index a03acd0d398a..695257ae64ac 100644
--- a/include/sound/seq_virmidi.h
+++ b/include/sound/seq_virmidi.h
@@ -60,6 +60,7 @@ struct snd_virmidi_dev {
int port; /* created/attached port */
unsigned int flags; /* SNDRV_VIRMIDI_* */
rwlock_t filelist_lock;
+ struct rw_semaphore filelist_sem;
struct list_head filelist;
};