kernel.git/sound/core/seq, branch linux-3.2.y

ALSA: seq: Clear client entry before deleting else at closing

2018-05-31T23:30:21Z

commit a2ff19f7b70118ced291a28d5313469914de451b upstream. When releasing a client, we need to clear the clienttab[] entry at first, then call snd_seq_queue_client_leave(). Otherwise, the in-flight cell in the queue might be picked up by the timer interrupt via snd_seq_check_queue() before calling snd_seq_queue_client_leave(), and it's delivered to another queue while the client is clearing queues. This may eventually result in an uncleared cell remaining in a queue, and the later snd_seq_pool_delete() may need to wait for a long time until the event gets really processed. By moving the clienttab[] clearance at the beginning of release, any event delivery of a cell belonging to this client will fail at a later point, since snd_seq_client_ptr() returns NULL. Thus the cell that was picked up by the timer interrupt will be returned immediately without further delivery, and the long stall of snd_seq_delete_pool() can be avoided, too. Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: seq: Fix possible UAF in snd_seq_check_queue()

2018-05-31T23:30:21Z

commit d0f833065221cbfcbadf19fd4102bcfa9330006a upstream. Although we've covered the races between concurrent write() and ioctl() in the previous patch series, there is still a possible UAF in the following scenario: A: user client closed B: timer irq -> snd_seq_release() -> snd_seq_timer_interrupt() -> snd_seq_free_client() -> snd_seq_check_queue() -> cell = snd_seq_prioq_cell_peek() -> snd_seq_prioq_leave() .... removing all cells -> snd_seq_pool_done() .... vfree() -> snd_seq_compare_tick_time(cell) ... Oops So the problem is that a cell is peeked and accessed without any protection until it's retrieved from the queue again via snd_seq_prioq_cell_out(). This patch tries to address it, also cleans up the code by a slight refactoring. snd_seq_prioq_cell_out() now receives an extra pointer argument. When it's non-NULL, the function checks the event timestamp with the given pointer. The caller needs to pass the right reference either to snd_seq_tick or snd_seq_realtime depending on the event timestamp type. A good news is that the above change allows us to remove the snd_seq_prioq_cell_peek(), too, thus the patch actually reduces the code size. Reviewed-by: Nicolai Stange Signed-off-by: Takashi Iwai [bwh: Backported to 3.2: Deleted function had different log message] Signed-off-by: Ben Hutchings

ALSA: seq: More protection for concurrent write and ioctl races

2018-05-31T23:30:02Z

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

ALSA: seq: correctly detect input buffer overflow

2018-05-31T23:30:02Z

commit 21fd3e956ee8a307a06bc6e095f5767a00eb2a7e upstream. snd_seq_event_dup returns -ENOMEM in some buffer-full conditions, but usually returns -EAGAIN. Make -EAGAIN trigger the overflow condition in snd_seq_fifo_event_in so that the fifo is cleared and -ENOSPC is returned to userspace as stated in the alsa-lib docs. Signed-off-by: Adam Goode Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: seq: Don't allow resizing pool in use

2018-05-31T23:30:02Z

commit d85739367c6d56e475c281945c68fdb05ca74b4c upstream. This is a fix for a (sort of) fallout in the recent commit d15d662e89fc ("ALSA: seq: Fix racy pool initializations") for CVE-2018-1000004. As the pool resize deletes the existing cells, it may lead to a race when another thread is writing concurrently, eventually resulting a UAF. A simple workaround is not to allow the pool resizing when the pool is in use. It's an invalid behavior in anyway. Fixes: d15d662e89fc ("ALSA: seq: Fix racy pool initializations") Reported-by: 范龙飞 Reported-by: Nicolai Stange Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: seq: Fix racy pool initializations

2018-05-31T23:30:02Z

commit d15d662e89fc667b90cd294b0eb45694e33144da upstream. ALSA sequencer core initializes the event pool on demand by invoking snd_seq_pool_init() when the first write happens and the pool is empty. Meanwhile user can reset the pool size manually via ioctl concurrently, and this may lead to UAF or out-of-bound accesses since the function tries to vmalloc / vfree the buffer. A simple fix is to just wrap the snd_seq_pool_init() call with the recently introduced client->ioctl_mutex; as the calls for snd_seq_pool_init() from other side are always protected with this mutex, we can avoid the race. Reported-by: 范龙飞 Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: seq: Remove spurious WARN_ON() at timer check

2018-03-03T15:50:41Z

commit 43a3542870328601be02fcc9d27b09db467336ef upstream. The use of snd_BUG_ON() in ALSA sequencer timer may lead to a spurious WARN_ON() when a slave timer is deployed as its backend and a corresponding master timer stops meanwhile. The symptom was triggered by syzkaller spontaneously. Since the NULL timer is valid there, rip off snd_BUG_ON(). Reported-by: syzbot Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: seq: Fix regression by incorrect ioctl_mutex usages

2018-03-03T15:50:37Z

This is the revised backport of the upstream commit b3defb791b26ea0683a93a4f49c77ec45ec96f10 We had another backport (e.g. 623e5c8ae32b in 4.4.115), but it applies the new mutex also to the code paths that are invoked via faked kernel-to-kernel ioctls. As reported recently, this leads to a deadlock at suspend (or other scenarios triggering the kernel sequencer client). This patch addresses the issue by taking the mutex only in the code paths invoked by user-space, just like the original fix patch does. Reported-and-tested-by: Andres Bertens Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings

ALSA: seq: Make ioctls race-free

2018-02-13T18:32:22Z

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 Reviewed-by: Kees Cook Reviewed-by: Greg Kroah-Hartman Signed-off-by: Takashi Iwai [bwh: Backported to 3.2: ioctl dispatch is done from snd_seq_do_ioctl(); take the mutex and add ret variable there.] Signed-off-by: Ben Hutchings

ALSA: seq: Fix OSS sysex delivery in OSS emulation

2018-01-01T20:51:02Z

commit 132d358b183ac6ad8b3fea32ad5e0663456d18d1 upstream. The SYSEX event delivery in OSS sequencer emulation assumed that the event is encoded in the variable-length data with the straight buffering. This was the normal behavior in the past, but during the development, the chained buffers were introduced for carrying more data, while the OSS code was left intact. As a result, when a SYSEX event with the chained buffer data is passed to OSS sequencer port, it may end up with the wrong memory access, as if it were having a too large buffer. This patch addresses the bug, by applying the buffer data expansion by the generic snd_seq_dump_var_event() helper function. Reported-by: syzbot Reported-by: Mark Salyzyn Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings