Fix racy pool initializations & Don't allow resizing pool in use & More protection for concurrent write and ioctl races in kernel-sound-ALSA-seq CVE-2018-7566
Tracked by Jolla
(Rejected)
asked 2018-06-25 11:09:22 +0300
This post is a wiki. Anyone with karma >75 is welcome to improve it.
The Linux kernel 4.15 has a Buffer Overflow via an SNDRV_SEQ_IOCTL_SET_CLIENT_POOL ioctl write operation to /dev/snd/seq by a local user.
Patches are available for 3.2 kernel: |1| |2| |3|
Files affected: kernel-adaptation-sbj-3.4.108.20171107.1/sound/core/seq/seq_clientmgr.c
/sound/core/seq/seq_fifo.c
/sound/core/seq/seq_memory.c
/sound/core/seq/seq_memory.h
so the patches should look like:
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -903,7 +903,8 @@ int snd_seq_dispatch_event(struct snd_seq_event_cell *cell, int atomic, int hop)
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;
@@ -943,7 +944,8 @@ static int snd_seq_client_enqueue_event(struct snd_seq_client *client,
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;
@@ -996,7 +998,7 @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
{
struct snd_seq_client *client = file->private_data;
int written = 0, len;
- int err = -EINVAL;
+ int err;
struct snd_seq_event event;
if (!(snd_seq_file_flags(file) & SNDRV_SEQ_LFLG_OUTPUT))
@@ -1012,11 +1014,15 @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
/* allocate the pool now if the pool is not allocated yet */
if (client->pool->size > 0 && !snd_seq_write_pool_allocated(client)) {
- if (snd_seq_pool_init(client->pool) < 0)
+ mutex_lock(&client->ioctl_mutex);
+ err = snd_seq_pool_init(client->pool);
+ mutex_unlock(&client->ioctl_mutex);
+ if (err < 0)
return -ENOMEM;
}
/* only process whole events */
+ err = -EINVAL;
while (count >= sizeof(struct snd_seq_event)) {
/* Read in the event header from the user */
len = sizeof(event);
@@ -1012,12 xxxx @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
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 */
@@ -1070,7 +1071,7 @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
/* 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;
@@ -1081,6 +1082,8 @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
written += len;
}
+ out:
+ mutex_unlock(&client->ioctl_mutex);
return written ? written : err;
}
@@ -1905,6 +1911,9 @@ static int snd_seq_ioctl_set_client_pool(struct snd_seq_client *client,
(! snd_seq_write_pool_allocated(client) ||
info.output_pool != client->pool->size)) {
if (snd_seq_write_pool_allocated(client)) {
+ /* is the pool in use? */
+ if (atomic_read(&client->pool->counter))
+ return -EBUSY;
/* remove all existing cells */
snd_seq_pool_mark_closing(client->pool);
snd_seq_queue_client_leave_cells(client->number);
@@ -2343,7 +2346,8 @@ static int kernel_client_enqueue(int client, struct snd_seq_event *ev,
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 e4389f1..9d429bc 100644
--- a/sound/core/seq/seq_fifo.c
+++ b/sound/core/seq/seq_fifo.c
@@ -125,7 +125,7 @@ int snd_seq_fifo_event_in(struct snd_seq_fifo *f,
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 6fc211d..ce5d003 100644
--- a/sound/core/seq/seq_memory.c
+++ b/sound/core/seq/seq_memory.c
@@ -221,7 +221,8 @@ void snd_seq_cell_free(struct snd_seq_event_cell * cell)
*/
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 @@ static int snd_seq_cell_alloc(struct snd_seq_pool *pool,
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 @@ __error:
*/
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 @@ int snd_seq_event_dup(struct snd_seq_pool *pool, struct snd_seq_event *event,
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 snd_seq_event_dup(struct snd_seq_pool *pool, struct snd_seq_event *event,
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 @@ struct snd_seq_pool {
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)