From: Takashi Iwai Date: Mon, 5 Mar 2018 21:06:09 +0000 (+0100) Subject: ALSA: seq: More protection for concurrent write and ioctl races X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=1a63d970eecf933973eae20b069f3755a7824b24 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 Reported-by: Nicolai Stange Reviewed-and-tested-by: Nicolai Stange Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 04522dc52e5c..12f80c570e84 100644 --- 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_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; @@ -945,7 +946,8 @@ 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; @@ -1014,12 +1016,11 @@ 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; } @@ -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 e4389f114415..9d429bc09538 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 6fc211dcb342..ce5d003cd8ec 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 32f959c17786..3abe306c394a 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)