kernel.git/sound/drivers/dummy.c, branch linux-3.2.y

ALSA: dummy: Fix a use-after-free at closing

2016-08-22T21:37:16Z

commit d5dbbe6569481bf12dcbe3e12cff72c5f78d272c upstream. syzkaller fuzzer spotted a potential use-after-free case in snd-dummy driver when hrtimer is used as backend: > ================================================================== > BUG: KASAN: use-after-free in rb_erase+0x1b17/0x2010 at addr ffff88005e5b6f68 > Read of size 8 by task syz-executor/8984 > ============================================================================= > BUG kmalloc-192 (Not tainted): kasan: bad access detected > ----------------------------------------------------------------------------- > > Disabling lock debugging due to kernel taint > INFO: Allocated in 0xbbbbbbbbbbbbbbbb age=18446705582212484632 > .... > [< none >] dummy_hrtimer_create+0x49/0x1a0 sound/drivers/dummy.c:464 > .... > INFO: Freed in 0xfffd8e09 age=18446705496313138713 cpu=2164287125 pid=-1 > [< none >] dummy_hrtimer_free+0x68/0x80 sound/drivers/dummy.c:481 > .... > Call Trace: > [] __asan_report_load8_noabort+0x3e/0x40 mm/kasan/report.c:333 > [< inline >] rb_set_parent include/linux/rbtree_augmented.h:111 > [< inline >] __rb_erase_augmented include/linux/rbtree_augmented.h:218 > [] rb_erase+0x1b17/0x2010 lib/rbtree.c:427 > [] timerqueue_del+0x78/0x170 lib/timerqueue.c:86 > [] __remove_hrtimer+0x90/0x220 kernel/time/hrtimer.c:903 > [< inline >] remove_hrtimer kernel/time/hrtimer.c:945 > [] hrtimer_try_to_cancel+0x22a/0x570 kernel/time/hrtimer.c:1046 > [] hrtimer_cancel+0x22/0x40 kernel/time/hrtimer.c:1066 > [] dummy_hrtimer_stop+0x91/0xb0 sound/drivers/dummy.c:417 > [] dummy_pcm_trigger+0x17f/0x1e0 sound/drivers/dummy.c:507 > [] snd_pcm_do_stop+0x160/0x1b0 sound/core/pcm_native.c:1106 > [] snd_pcm_action_single+0x76/0x120 sound/core/pcm_native.c:956 > [] snd_pcm_action+0x231/0x290 sound/core/pcm_native.c:974 > [< inline >] snd_pcm_stop sound/core/pcm_native.c:1139 > [] snd_pcm_drop+0x12d/0x1d0 sound/core/pcm_native.c:1784 > [] snd_pcm_common_ioctl1+0xfae/0x2150 sound/core/pcm_native.c:2805 > [] snd_pcm_capture_ioctl1+0x2a1/0x5e0 sound/core/pcm_native.c:2976 > [] snd_pcm_kernel_ioctl+0x11c/0x160 sound/core/pcm_native.c:3020 > [] snd_pcm_oss_sync+0x3a4/0xa30 sound/core/oss/pcm_oss.c:1693 > [] snd_pcm_oss_release+0x1ad/0x280 sound/core/oss/pcm_oss.c:2483 > ..... A workaround is to call hrtimer_cancel() in dummy_hrtimer_sync() which is called certainly before other blocking ops. Reported-by: Dmitry Vyukov Tested-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

ALSA: dummy: Implement timer backend switching more safely

2016-02-27T14:28:47Z

commit ddce57a6f0a2d8d1bfacfa77f06043bc760403c2 upstream. Currently the selected timer backend is referred at any moment from the running PCM callbacks. When the backend is switched, it's possible to lead to inconsistency from the running backend. This was pointed by syzkaller fuzzer, and the commit [7ee96216c31a: ALSA: dummy: Disable switching timer backend via sysfs] disabled the dynamic switching for avoiding the crash. This patch improves the handling of timer backend switching. It keeps the reference to the selected backend during the whole operation of an opened stream so that it won't be changed by other streams. Together with this change, the hrtimer parameter is reenabled as writable now. NOTE: this patch also turned out to fix the still remaining race. Namely, ops was still replaced dynamically at dummy_pcm_open: static int dummy_pcm_open(struct snd_pcm_substream *substream) { .... dummy->timer_ops = &dummy_systimer_ops; if (hrtimer) dummy->timer_ops = &dummy_hrtimer_ops; Since dummy->timer_ops is common among all streams, and when the replacement happens during accesses of other streams, it may lead to a crash. This was actually triggered by syzkaller fuzzer and KASAN. This patch rewrites the code not to use the ops shared by all streams any longer, too. BugLink: http://lkml.kernel.org/r/CACT4Y+aZ+xisrpuM6cOXbL21DuM0yVxPYXf4cD4Md9uw0C3dBQ@mail.gmail.com Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings

ALSA: dummy: Disable switching timer backend via sysfs

2016-02-27T14:28:44Z

commit 7ee96216c31aabe1eb42fb91ff50dae9fcd014b2 upstream. ALSA dummy driver can switch the timer backend between system timer and hrtimer via its hrtimer module option. This can be also switched dynamically via sysfs, but it may lead to a memory corruption when switching is done while a PCM stream is running; the stream instance for the newly switched timer method tries to access the memory that was allocated by another timer method although the sizes differ. As the simplest fix, this patch just disables the switch via sysfs by dropping the writable bit. BugLink: http://lkml.kernel.org/r/CACT4Y+ZGEeEBntHW5WHn2GoeE0G_kRrCmUh6=dWyy-wfzvuJLg@mail.gmail.com Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings

sound: fix drivers needing module.h not moduleparam.h

2011-10-31T23:31:19Z

The implicit presence of module.h lured several users into incorrectly thinking that they only needed/used modparam.h but once we clean up the module.h presence, these will show up as build failures, so fix 'em now. Signed-off-by: Paul Gortmaker

ALSA: dummy driver - add model parameter

2010-02-02T16:50:57Z

This is a cleanup for the dummy driver. The model kernel module parameter is introduced to select the soundcard emulation. Signed-off-by: Jaroslav Kysela

ALSA: dummy - Fix descriptions of pcm_substreams parameter

2009-11-02T13:11:55Z

Now up to 128 substreams are supported. Reported-by: Adrian Bridgett Signed-off-by: Takashi Iwai

ALSA: sound: Move dereference after NULL test and drop unnecessary NULL tests

2009-10-30T11:01:27Z

In pcm.c, if the NULL test on pcm is needed, then the dereference should be after the NULL test. In dummy.c and ali5451.c, the context of the calls to snd_card_dummy_new_mixer and snd_ali_free_voice show that dummy and pvoice, respectively cannot be NULL. A simplified version of the semantic match that detects this problem is as follows (http://coccinelle.lip6.fr/): // @match exists@ expression x, E; identifier fld; @@ * x->fld ... when != \(x = E\|&x\) * x == NULL // Signed-off-by: Julia Lawall Signed-off-by: Takashi Iwai

ALSA: dummy - Increase MAX_PCM_SUBSTREAMS to 128

2009-09-08T16:15:17Z

Increase the limit of PCM substreams to 128. The default value is unchanged; only the max accept value is increased. Signed-off-by: Takashi Iwai

ALSA: dummy - Add debug proc file

2009-09-08T12:46:49Z

Added the debug proc file to see or change the snd_pcm_hardware fields to emulate. The parameters can be changed by writing to a proc file like: # echo periods_min 4 > /proc/asound/card1/dummy_pcm Signed-off-by: Takashi Iwai

ALSA: dummy - Fake buffer allocations

2009-09-07T07:01:10Z

Instead of allocating the real buffers, use a fake buffer and ignore read/write in the dummy driver so that we can save the resources. For mmap, a single page (unique to the direction, though) is reused to all buffers. When the app requires to read/write the real buffers, pass fake_buffer=0 module option at loading time. This will get back to the old behavior. Signed-off-by: Takashi Iwai