3.2.102-rc1 review patch. If anyone has any objections, please let me know.
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From: Takashi Iwai tiwai@suse.de
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 Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Ben Hutchings ben@decadent.org.uk --- sound/core/seq/seq_clientmgr.c | 18 +++++++++++------- sound/core/seq/seq_fifo.c | 2 +- sound/core/seq/seq_memory.c | 14 ++++++++++---- sound/core/seq/seq_memory.h | 3 ++- 4 files changed, 24 insertions(+), 13 deletions(-)
--- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -907,7 +907,8 @@ int snd_seq_dispatch_event(struct snd_se 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; @@ -945,7 +946,8 @@ static int snd_seq_client_enqueue_event( 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;
@@ -1014,12 +1016,11 @@ static ssize_t snd_seq_write(struct file 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 /* 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 written += len; }
+ out: + mutex_unlock(&client->ioctl_mutex); return written ? written : err; }
@@ -2343,7 +2346,8 @@ static int kernel_client_enqueue(int cli 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; --- 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 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); --- 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_ev */ 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 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_poo 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_poo 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) --- 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)