From 556c435462e3c3ea74ae1a58aba08aa3a4027959 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 9 Apr 2019 17:35:22 +0200 Subject: [PATCH] ALSA: seq: Protect in-kernel ioctl calls with mutex [ Upstream commit feb689025fbb6f0aa6297d3ddf97de945ea4ad32 ] ALSA OSS sequencer calls the ioctl function indirectly via snd_seq_kernel_client_ctl(). While we already applied the protection against races between the normal ioctls and writes via the client's ioctl_mutex, this code path was left untouched. And this seems to be the cause of still remaining some rare UAF as spontaneously triggered by syzkaller. For the sake of robustness, wrap the ioctl_mutex also for the call via snd_seq_kernel_client_ctl(), too. Reported-by: syzbot+e4c8abb920efa77bace9@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai Signed-off-by: Sasha Levin --- sound/core/seq/seq_clientmgr.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 09491b27092e..3b1b2e9fb33e 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -2354,14 +2354,19 @@ int snd_seq_kernel_client_ctl(int clientid, unsigned int cmd, void *arg) { const struct ioctl_handler *handler; struct snd_seq_client *client; + int err; client = clientptr(clientid); if (client == NULL) return -ENXIO; for (handler = ioctl_handlers; handler->cmd > 0; ++handler) { - if (handler->cmd == cmd) - return handler->func(client, arg); + if (handler->cmd == cmd) { + mutex_lock(&client->ioctl_mutex); + err = handler->func(client, arg); + mutex_unlock(&client->ioctl_mutex); + return err; + } } pr_debug("ALSA: seq unknown ioctl() 0x%x (type='%c', number=0x%02x)\n",