4.4-stable review patch. If anyone has any objections, please let me know.
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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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- sound/core/seq/seq_clientmgr.c | 10 ++++++++-- sound/core/seq/seq_clientmgr.h | 1 + 2 files changed, 9 insertions(+), 2 deletions(-)
--- 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 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_s 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_s 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)); --- 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 */