ALSA: seq: More protection for concurrent write and ioctl races
commit 7bd80091567789f1c0cb70eb4737aac8bcd2b6b9 upstream.
This patch is an attempt for further hardening against races between
the concurrent write and ioctls. The previous fix d15d662e89fc
("ALSA: seq: Fix racy pool initializations") covered the race of the
pool initialization at writer and the pool resize ioctl by the
client->ioctl_mutex (CVE-2018-1000004). However, basically this mutex
should be applied more widely to the whole write operation for
avoiding the unexpected pool operations by another thread.
The only change outside snd_seq_write() is the additional mutex
argument to helper functions, so that we can unlock / relock the given
mutex temporarily during schedule() call for blocking write.
Fixes: d15d662e89fc ("ALSA: seq: Fix racy pool initializations")
Reported-by: 范龙飞 <long7573@126.com>
Reported-by: Nicolai Stange <nstange@suse.de>
Reviewed-and-tested-by: Nicolai Stange <nstange@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index ec4d42b..799ad3e 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -906,7 +906,8 @@
static int snd_seq_client_enqueue_event(struct snd_seq_client *client,
struct snd_seq_event *event,
struct file *file, int blocking,
- int atomic, int hop)
+ int atomic, int hop,
+ struct mutex *mutexp)
{
struct snd_seq_event_cell *cell;
int err;
@@ -944,7 +945,8 @@
return -ENXIO; /* queue is not allocated */
/* allocate an event cell */
- err = snd_seq_event_dup(client->pool, event, &cell, !blocking || atomic, file);
+ err = snd_seq_event_dup(client->pool, event, &cell, !blocking || atomic,
+ file, mutexp);
if (err < 0)
return err;
@@ -1013,12 +1015,11 @@
return -ENXIO;
/* allocate the pool now if the pool is not allocated yet */
+ mutex_lock(&client->ioctl_mutex);
if (client->pool->size > 0 && !snd_seq_write_pool_allocated(client)) {
- mutex_lock(&client->ioctl_mutex);
err = snd_seq_pool_init(client->pool);
- mutex_unlock(&client->ioctl_mutex);
if (err < 0)
- return -ENOMEM;
+ goto out;
}
/* only process whole events */
@@ -1069,7 +1070,7 @@
/* ok, enqueue it */
err = snd_seq_client_enqueue_event(client, &event, file,
!(file->f_flags & O_NONBLOCK),
- 0, 0);
+ 0, 0, &client->ioctl_mutex);
if (err < 0)
break;
@@ -1080,6 +1081,8 @@
written += len;
}
+ out:
+ mutex_unlock(&client->ioctl_mutex);
return written ? written : err;
}
@@ -2262,7 +2265,8 @@
if (! cptr->accept_output)
result = -EPERM;
else /* send it */
- result = snd_seq_client_enqueue_event(cptr, ev, file, blocking, atomic, hop);
+ result = snd_seq_client_enqueue_event(cptr, ev, file, blocking,
+ atomic, hop, NULL);
snd_seq_client_unlock(cptr);
return result;
diff --git a/sound/core/seq/seq_fifo.c b/sound/core/seq/seq_fifo.c
index 3490d21..9acbed1 100644
--- a/sound/core/seq/seq_fifo.c
+++ b/sound/core/seq/seq_fifo.c
@@ -123,7 +123,7 @@
return -EINVAL;
snd_use_lock_use(&f->use_lock);
- err = snd_seq_event_dup(f->pool, event, &cell, 1, NULL); /* always non-blocking */
+ err = snd_seq_event_dup(f->pool, event, &cell, 1, NULL, NULL); /* always non-blocking */
if (err < 0) {
if ((err == -ENOMEM) || (err == -EAGAIN))
atomic_inc(&f->overflow);
diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c
index 5847c44..4c8cbcd 100644
--- a/sound/core/seq/seq_memory.c
+++ b/sound/core/seq/seq_memory.c
@@ -221,7 +221,8 @@
*/
static int snd_seq_cell_alloc(struct snd_seq_pool *pool,
struct snd_seq_event_cell **cellp,
- int nonblock, struct file *file)
+ int nonblock, struct file *file,
+ struct mutex *mutexp)
{
struct snd_seq_event_cell *cell;
unsigned long flags;
@@ -245,7 +246,11 @@
set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&pool->output_sleep, &wait);
spin_unlock_irq(&pool->lock);
+ if (mutexp)
+ mutex_unlock(mutexp);
schedule();
+ if (mutexp)
+ mutex_lock(mutexp);
spin_lock_irq(&pool->lock);
remove_wait_queue(&pool->output_sleep, &wait);
/* interrupted? */
@@ -288,7 +293,7 @@
*/
int snd_seq_event_dup(struct snd_seq_pool *pool, struct snd_seq_event *event,
struct snd_seq_event_cell **cellp, int nonblock,
- struct file *file)
+ struct file *file, struct mutex *mutexp)
{
int ncells, err;
unsigned int extlen;
@@ -305,7 +310,7 @@
if (ncells >= pool->total_elements)
return -ENOMEM;
- err = snd_seq_cell_alloc(pool, &cell, nonblock, file);
+ err = snd_seq_cell_alloc(pool, &cell, nonblock, file, mutexp);
if (err < 0)
return err;
@@ -331,7 +336,8 @@
int size = sizeof(struct snd_seq_event);
if (len < size)
size = len;
- err = snd_seq_cell_alloc(pool, &tmp, nonblock, file);
+ err = snd_seq_cell_alloc(pool, &tmp, nonblock, file,
+ mutexp);
if (err < 0)
goto __error;
if (cell->event.data.ext.ptr == NULL)
diff --git a/sound/core/seq/seq_memory.h b/sound/core/seq/seq_memory.h
index 32f959c..3abe306 100644
--- a/sound/core/seq/seq_memory.h
+++ b/sound/core/seq/seq_memory.h
@@ -66,7 +66,8 @@
void snd_seq_cell_free(struct snd_seq_event_cell *cell);
int snd_seq_event_dup(struct snd_seq_pool *pool, struct snd_seq_event *event,
- struct snd_seq_event_cell **cellp, int nonblock, struct file *file);
+ struct snd_seq_event_cell **cellp, int nonblock,
+ struct file *file, struct mutex *mutexp);
/* return number of unused (free) cells */
static inline int snd_seq_unused_cells(struct snd_seq_pool *pool)