linux.git/sound/core/seq/seq_clientmgr.c, branch v4.14.229

ALSA: seq: Fix concurrent access to queue current tick/time

2020-02-28T15:36:16+00:00

commit dc7497795e014d84699c3b8809ed6df35352dd74 upstream.

snd_seq_check_queue() passes the current tick and time of the given
queue as a pointer to snd_seq_prioq_cell_out(), but those might be
updated concurrently by the seq timer update.

Fix it by retrieving the current tick and time via the proper helper
functions at first, and pass those values to snd_seq_prioq_cell_out()
later in the loops.

snd_seq_timer_get_cur_time() takes a new argument and adjusts with the
current system time only when it's requested so; this update isn't
needed for snd_seq_check_queue(), as it's called either from the
interrupt handler or right after queuing.

Also, snd_seq_timer_get_cur_tick() is changed to read the value in the
spinlock for the concurrency, too.

Reported-by: syzbot+fd5e0eaa1a32999173b2@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20200214111316.26939-3-tiwai@suse.de
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman

ALSA: seq: Fix potential concurrent access to the deleted pool

2019-09-06T08:20:52+00:00

commit 75545304eba6a3d282f923b96a466dc25a81e359 upstream.

The input pool of a client might be deleted via the resize ioctl, the
the access to it should be covered by the proper locks.  Currently the
only missing place is the call in snd_seq_ioctl_get_client_pool(), and
this patch papers over it.

Reported-by: syzbot+4a75454b9ca2777f35c7@syzkaller.appspotmail.com
Cc: 
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman

ALSA: seq: Break too long mutex context in the write loop

2019-07-31T05:28:38+00:00

commit ede34f397ddb063b145b9e7d79c6026f819ded13 upstream.

The fix for the racy writes and ioctls to sequencer widened the
application of client->ioctl_mutex to the whole write loop.  Although
it does unlock/relock for the lengthy operation like the event dup,
the loop keeps the ioctl_mutex for the whole time in other
situations.  This may take quite long time if the user-space would
give a huge buffer, and this is a likely cause of some weird behavior
spotted by syzcaller fuzzer.

This patch puts a simple workaround, just adding a mutex break in the
loop when a large number of events have been processed.  This
shouldn't hit any performance drop because the threshold is set high
enough for usual operations.

Fixes: 7bd800915677 ("ALSA: seq: More protection for concurrent write and ioctl races")
Reported-by: syzbot+97aae04ce27e39cbfca9@syzkaller.appspotmail.com
Reported-by: syzbot+4c595632b98bb8ffcc66@syzkaller.appspotmail.com
Cc: 
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman

Revert "ALSA: seq: Protect in-kernel ioctl calls with mutex"

2019-06-19T06:20:56+00:00

[ Upstream commit f0654ba94e33699b295ce4f3dc73094db6209035 ]

This reverts commit feb689025fbb6f0aa6297d3ddf97de945ea4ad32.

The fix attempt was incorrect, leading to the mutex deadlock through
the close of OSS sequencer client.  The proper fix needs more
consideration, so let's revert it now.

Fixes: feb689025fbb ("ALSA: seq: Protect in-kernel ioctl calls with mutex")
Reported-by: syzbot+47ded6c0f23016cde310@syzkaller.appspotmail.com
Signed-off-by: Takashi Iwai 
Signed-off-by: Sasha Levin

ALSA: seq: Fix race of get-subscription call vs port-delete ioctls

2019-06-19T06:20:56+00:00

[ Upstream commit 2eabc5ec8ab4d4748a82050dfcb994119b983750 ]

The snd_seq_ioctl_get_subscription() retrieves the port subscriber
information as a pointer, while the object isn't protected, hence it
may be deleted before the actual reference.  This race was spotted by
syzkaller and may lead to a UAF.

The fix is simply copying the data in the lookup function that
performs in the rwsem to protect against the deletion.

Reported-by: syzbot+9437020c82413d00222d@syzkaller.appspotmail.com
Signed-off-by: Takashi Iwai 
Signed-off-by: Sasha Levin

ALSA: seq: Protect in-kernel ioctl calls with mutex

2019-06-19T06:20:56+00:00

[ 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

ALSA: seq: Fix OOB-reads from strlcpy

2019-04-17T06:37:50+00:00

commit 212ac181c158c09038c474ba68068be49caecebb upstream.

When ioctl calls are made with non-null-terminated userspace strings,
strlcpy causes an OOB-read from within strlen. Fix by changing to use
strscpy instead.

Signed-off-by: Zubin Mithra 
Reviewed-by: Guenter Roeck 
Cc: 
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman

ALSA: seq: Fix UBSAN warning at SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT ioctl

2018-08-24T11:09:05+00:00

[ Upstream commit c9a4c63888dbb79ce4d068ca1dd8b05bc3f156b1 ]

The kernel may spew a WARNING with UBSAN undefined behavior at
handling ALSA sequencer ioctl SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT:

UBSAN: Undefined behaviour in sound/core/seq/seq_clientmgr.c:2007:14
signed integer overflow:
2147483647 + 1 cannot be represented in type 'int'
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x122/0x1c8 lib/dump_stack.c:113
 ubsan_epilogue+0x12/0x86 lib/ubsan.c:159
 handle_overflow+0x1c2/0x21f lib/ubsan.c:190
  __ubsan_handle_add_overflow+0x2a/0x31 lib/ubsan.c:198
 snd_seq_ioctl_query_next_client+0x1ac/0x1d0 sound/core/seq/seq_clientmgr.c:2007
 snd_seq_ioctl+0x264/0x3d0 sound/core/seq/seq_clientmgr.c:2144
 ....

It happens only when INT_MAX is passed there, as we're incrementing it
unconditionally.  So the fix is trivial, check the value with
INT_MAX.  Although the bug itself is fairly harmless, it's better to
fix it so that fuzzers won't hit this again later.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200211
Signed-off-by: Takashi Iwai 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

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

2018-03-21T11:06:42+00:00

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.

Cc: 
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman

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

2018-03-15T09:54:34+00:00

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 
Cc: 
Signed-off-by: Takashi Iwai 
Signed-off-by: Greg Kroah-Hartman