From: Takashi Iwai tiwai@suse.de

commit b3defb791b26ea0683a93a4f49c77ec45ec96f10 upstream.

The ALSA sequencer ioctls have no protection against racy calls while the concurrent operations may lead to interfere with each other. As reported recently, for example, the concurrent calls of setting client pool with a combination of write calls may lead to either the unkillable dead-lock or UAF.

As a slightly big hammer solution, this patch introduces the mutex to make each ioctl exclusive. Although this may reduce performance via parallel ioctl calls, usually it's not demanded for sequencer usages, hence it should be negligible.

Reported-by: Luo Quan a4651386@163.com Reviewed-by: Kees Cook keescook@chromium.org Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Takashi Iwai tiwai@suse.de [bwh: Backported to 4.4: ioctl dispatch is done from snd_seq_do_ioctl(); take the mutex and add ret variable there.] Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk --- v2: Restore Takashi as author

sound/core/seq/seq_clientmgr.c | 10 ++++++++-- sound/core/seq/seq_clientmgr.h | 1 + 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index b36de76f24e2..7bb9fe7a2c8e 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -236,6 +236,7 @@ static struct snd_seq_client *seq_create_client1(int client_index, int poolsize) rwlock_init(&client->ports_lock); mutex_init(&client->ports_mutex); INIT_LIST_HEAD(&client->ports_list_head); + mutex_init(&client->ioctl_mutex);

/* find free slot in the client table */ spin_lock_irqsave(&clients_lock, flags); @@ -2195,6 +2196,7 @@ static int snd_seq_do_ioctl(struct snd_seq_client *client, unsigned int cmd, void __user *arg) { struct seq_ioctl_table *p; + int ret;

switch (cmd) { case SNDRV_SEQ_IOCTL_PVERSION: @@ -2208,8 +2210,12 @@ static int snd_seq_do_ioctl(struct snd_seq_client *client, unsigned int cmd, if (! arg) return -EFAULT; for (p = ioctl_tables; p->cmd; p++) { - if (p->cmd == cmd) - return p->func(client, arg); + if (p->cmd == cmd) { + mutex_lock(&client->ioctl_mutex); + ret = p->func(client, arg); + mutex_unlock(&client->ioctl_mutex); + return ret; + } } pr_debug("ALSA: seq unknown ioctl() 0x%x (type='%c', number=0x%02x)\n", cmd, _IOC_TYPE(cmd), _IOC_NR(cmd)); diff --git a/sound/core/seq/seq_clientmgr.h b/sound/core/seq/seq_clientmgr.h index 20f0a725ec7d..91f8f165bfdc 100644 --- a/sound/core/seq/seq_clientmgr.h +++ b/sound/core/seq/seq_clientmgr.h @@ -59,6 +59,7 @@ struct snd_seq_client { struct list_head ports_list_head; rwlock_t ports_lock; struct mutex ports_mutex; + struct mutex ioctl_mutex; int convert32; /* convert 32->64bit */

/* output pool */