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authorTakashi Iwai <tiwai@suse.de>2017-03-21 13:56:04 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-03-30 09:41:23 +0200
commitca79952dfc63eb5f4f731600b08c2b012b773fa7 (patch)
treecb259bc062ab2687f1b2bfb7afd657960e74bf27 /sound
parent425823646eaed17448ce23101204973d48f376fb (diff)
downloadlinux-aarch64-ca79952dfc63eb5f4f731600b08c2b012b773fa7.tar.gz
ALSA: seq: Fix racy cell insertions during snd_seq_pool_done()
commit c520ff3d03f0b5db7146d9beed6373ad5d2a5e0e upstream. When snd_seq_pool_done() is called, it marks the closing flag to refuse the further cell insertions. But snd_seq_pool_done() itself doesn't clear the cells but just waits until all cells are cleared by the caller side. That is, it's racy, and this leads to the endless stall as syzkaller spotted. This patch addresses the racy by splitting the setup of pool->closing flag out of snd_seq_pool_done(), and calling it properly before snd_seq_pool_done(). BugLink: http://lkml.kernel.org/r/CACT4Y+aqqy8bZA1fFieifNxR2fAfFQQABcBHj801+u5ePV0URw@mail.gmail.com Reported-and-tested-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound')
-rw-r--r--sound/core/seq/seq_clientmgr.c1
-rw-r--r--sound/core/seq/seq_fifo.c3
-rw-r--r--sound/core/seq/seq_memory.c17
-rw-r--r--sound/core/seq/seq_memory.h1
4 files changed, 18 insertions, 4 deletions
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 4c935202ce23..f3b1d7f50b81 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1832,6 +1832,7 @@ static int snd_seq_ioctl_set_client_pool(struct snd_seq_client *client,
info->output_pool != client->pool->size)) {
if (snd_seq_write_pool_allocated(client)) {
/* remove all existing cells */
+ snd_seq_pool_mark_closing(client->pool);
snd_seq_queue_client_leave_cells(client->number);
snd_seq_pool_done(client->pool);
}
diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c
index 86240d02b530..3f4efcb85df5 100644
--- a/sound/core/seq/seq_fifo.c
+++ b/sound/core/seq/seq_fifo.c
@@ -70,6 +70,9 @@ void snd_seq_fifo_delete(struct snd_seq_fifo **fifo)
return;
*fifo = NULL;
+ if (f->pool)
+ snd_seq_pool_mark_closing(f->pool);
+
snd_seq_fifo_clear(f);
/* wake up clients if any */
diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c
index dfa5156f3585..5847c4475bf3 100644
--- a/sound/core/seq/seq_memory.c
+++ b/sound/core/seq/seq_memory.c
@@ -414,6 +414,18 @@ int snd_seq_pool_init(struct snd_seq_pool *pool)
return 0;
}
+/* refuse the further insertion to the pool */
+void snd_seq_pool_mark_closing(struct snd_seq_pool *pool)
+{
+ unsigned long flags;
+
+ if (snd_BUG_ON(!pool))
+ return;
+ spin_lock_irqsave(&pool->lock, flags);
+ pool->closing = 1;
+ spin_unlock_irqrestore(&pool->lock, flags);
+}
+
/* remove events */
int snd_seq_pool_done(struct snd_seq_pool *pool)
{
@@ -424,10 +436,6 @@ int snd_seq_pool_done(struct snd_seq_pool *pool)
return -EINVAL;
/* wait for closing all threads */
- spin_lock_irqsave(&pool->lock, flags);
- pool->closing = 1;
- spin_unlock_irqrestore(&pool->lock, flags);
-
if (waitqueue_active(&pool->output_sleep))
wake_up(&pool->output_sleep);
@@ -484,6 +492,7 @@ int snd_seq_pool_delete(struct snd_seq_pool **ppool)
*ppool = NULL;
if (pool == NULL)
return 0;
+ snd_seq_pool_mark_closing(pool);
snd_seq_pool_done(pool);
kfree(pool);
return 0;
diff --git a/sound/core/seq/seq_memory.h b/sound/core/seq/seq_memory.h
index 4a2ec779b8a7..32f959c17786 100644
--- a/sound/core/seq/seq_memory.h
+++ b/sound/core/seq/seq_memory.h
@@ -84,6 +84,7 @@ static inline int snd_seq_total_cells(struct snd_seq_pool *pool)
int snd_seq_pool_init(struct snd_seq_pool *pool);
/* done pool - free events */
+void snd_seq_pool_mark_closing(struct snd_seq_pool *pool);
int snd_seq_pool_done(struct snd_seq_pool *pool);
/* create pool */