syzbot


Applied filters: Label=subsystems:sound (drop)
Title Repro Cause bisect Fix bisect Count Last Reported Patched Closed Patch
BUG: unable to handle kernel paging request in snd_pcm_format_set_silence (2) sound C 4 29d 43d 27/28 never 93a81ca06577 ALSA: pcm: Fix race of buffer access at PCM OSS layer
WARNING: ODEBUG bug in snd_rawmidi_free usb sound C error 1 43d 39d 27/28 never 0718a78f6a9f ALSA: usb-audio: Kill timer properly at removal
possible deadlock in __snd_timer_user_ioctl sound 1 91d 87d 28/28 6d00h 3424c8f53bc6 ALSA: timer: Don't take register_mutex with copy_from/to_user()
KCSAN: data-race in snd_seq_poll / snd_seq_pool_init sound 3 90d 102d 28/28 6d00h e3cd33ab17c3 ALSA: seq: Improve data consistency at polling
BUG: sleeping function called from invalid context in snd_card_locked sound 1 111d 107d 28/28 6d00h c9ce148ea753 ALSA: seq: Avoid module auto-load handling at event delivery
kernel BUG in filemap_fault sound C done 138 10d 108d 28/28 6d00h 10a77965760c batman-adv: Fix double-hold of meshif when getting enabled
BUG: sleeping function called from invalid context in vfree sound 1 203d 203d 28/28 41d 20c0c49720dc ALSA: rawmidi: Fix kvfree() call in spinlock
WARNING in snd_ctl_led_register sound 1 193d 189d 28/28 41d b2e538a9827d ALSA: control: Avoid WARN() for symlink errors
kernel BUG in snd_pcm_mmap_data_fault sound 1 271d 267d 28/28 41d d2913a07d903 ALSA: pcm: Add sanity NULL check for the default mmap fault handler
INFO: task hung in snd_card_free sound C error 24 210d 225d 28/28 182d dafb28f02be4 ALSA: usx2y: Use snd_card_free_when_closed() at disconnection
KMSAN: uninit-value in line6_midibuf_read usb sound C 357 265d 327d 28/28 256d 15b7a03205b3 ALSA: line6: Fix racy access to midibuf
UBSAN: shift-out-of-bounds in parse_audio_unit sound C error 3 338d 336d 27/28 306d 2f38cf730cae ALSA: usb: Fix UBSAN warning in parse_audio_unit()
inconsistent lock state in valid_state (2) sound C inconclusive 57405 371d 495d 25/28 370d b79491896151 dma-buf/sw-sync: don't enable IRQ from sync_print_obj()
INFO: rcu detected stall in snd_timer_user_release (3) sound C inconclusive 3 404d 412d 25/28 370d 4a63bd179fa8 ALSA: timer: Set lower bound of start tick time
KMSAN: uninit-value in line6_pod_process_message sound C 5 440d 441d 25/28 389d c4e51e424e2c ALSA: line6: Zero-initialize message buffers
inconsistent lock state in snd_hrtimer_callback (2) sound C 2600 426d 428d 25/28 420d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
possible deadlock in snd_timer_close_locked (2) sound C done 3036 426d 428d 25/28 420d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
inconsistent lock state in snd_timer_interrupt (3) sound C 710 426d 431d 25/28 420d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
INFO: rcu detected stall in snd_timer_user_release (2) sound C 7 420d 433d 25/28 420d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
possible deadlock in _snd_pcm_stream_lock_irqsave (5) sound C 5210 426d 428d 25/28 420d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
inconsistent lock state in snd_timer_interrupt (2) sound C done 208 431d 432d 25/28 431d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
KMSAN: uninit-value in bcmp (2) sound btrfs C 7 497d 519d 25/28 432d fde2497d2bc3 fat: fix uninitialized field in nostale filehandles
possible deadlock in _snd_pcm_stream_lock_irqsave (4) sound C 24677 432d 454d 25/28 432d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
possible deadlock in snd_pcm_period_elapsed (4) sound C done 90659 432d 458d 25/28 432d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
inconsistent lock state in snd_timer_interrupt sound C 1927 432d 454d 25/28 432d 587d67fd929a ALSA: timer: Fix missing irq-disable at closing
memory leak in snd_seq_create_port sound C 1 705d 701d 23/28 613d 057849ccc3d8 ALSA: seq: Fix memory leak at error path in snd_seq_create_port()
possible deadlock in snd_timer_interrupt (2) sound C error 29 1042d 1302d 22/28 843d 95cc637c1afd ALSA: timer: Use deferred fasync helper
KASAN: use-after-free Read in __snd_rawmidi_transmit_peek sound usb syz error 48 1044d 1155d 22/28 843d 0665886ad139 ALSA: usb-audio: Clear MIDI port active flag after draining
KASAN: use-after-free Read in snd_rawmidi_transmit usb sound C done done 7 1111d 1145d 22/28 843d 0125de38122f ALSA: usb-audio: Cancel pending work at closing a MIDI substream
possible deadlock in __snd_pcm_lib_xfer sound C unreliable 3 1175d 1174d 22/28 843d bc55cfd5718c ALSA: pcm: Fix potential AB/BA lock with buffer_mutex and mmap_lock
KASAN: null-ptr-deref Write in snd_pcm_format_set_silence sound C unreliable 8 1020d 1164d 22/28 843d 2f7a26abb824 ALSA: pcm: Test for "silence" field in struct "pcm_format_data"
KASAN: use-after-free Read in __snd_rawmidi_transmit_ack sound 1 1122d 1118d 22/28 843d 0125de38122f ALSA: usb-audio: Cancel pending work at closing a MIDI substream
WARNING: kmalloc bug in snd_pcm_plugin_alloc (2) sound C done 2 1191d 1187d 22/28 843d efb6402c3c4a ALSA: oss: Fix PCM OSS buffer allocation overflow
possible deadlock in snd_pcm_period_elapsed (3) sound C inconclusive 23 1040d 1265d 22/28 843d 96b097091c66 ALSA: pcm: Use deferred fasync helper
KASAN: use-after-free Read in snd_mixer_oss_get_volume1 sound C inconclusive 1 1339d 1335d 20/28 1196d 411cef6adfb3 ALSA: mixer: oss: Fix racy access to slots
WARNING: kmalloc bug in snd_pcm_plugin_alloc sound 4 1216d 1298d 20/28 1196d 9d2479c96087 ALSA: pcm: oss: Fix negative period/buffer sizes 8839c8c0f77a ALSA: pcm: oss: Limit the period size to 16MB
possible deadlock in snd_mixer_oss_ioctl1 sound C done 149 1328d 1331d 20/28 1196d 3ab799201845 ALSA: mixer: fix deadlock in snd_mixer_oss_set_volume
INFO: rcu detected stall in snd_seq_write (2) sound syz done 21 1311d 1323d 20/28 1196d 6fadb494a638 ALSA: seq: Set upper limit of processed events
KMSAN: uninit-value in snd_rawmidi_ioctl sound C 1506 1213d 1276d 20/28 1196d 39a8fc4971a0 ALSA: rawmidi - fix the uninitalized user_pversion
possible deadlock in snd_timer_interrupt sound C done 41 1321d 1422d 20/28 1314d f671a691e299 fcntl: fix potential deadlocks for &fown_struct.lock
KASAN: use-after-free Read in snd_seq_timer_interrupt (2) sound C inconclusive 2 1471d 1470d 20/28 1314d 83e197a8414c ALSA: seq: Fix race of snd_seq_timer_open()
UBSAN: shift-out-of-bounds in snd_timer_user_ccallback sound 1 1479d 1475d 20/28 1314d 9c1fe96bded9 ALSA: timer: Fix master timer notification
general protection fault in usb_audio_probe usb sound C done 360 1559d 1560d 20/28 1528d 30dea07180de ALSA: usb-audio: fix NULL ptr dereference in usb_audio_probe
KASAN: use-after-free Read in usb_audio_disconnect sound usb C done 15 1559d 1560d 20/28 1528d c5aa956eaeb0 ALSA: usb-audio: fix use after free in usb_audio_disconnect
KCSAN: data-race in snd_rawmidi_transmit / snd_rawmidi_write sound 232 1592d 1768d 19/28 1559d 88a06d6fd6b3 ALSA: rawmidi: Access runtime->avail always in spinlock
UBSAN: shift-out-of-bounds in parse_audio_format_i sound usb C error 19 1644d 1650d 19/28 1559d 175b8d89fe29 ALSA: pcm: oss: Fix potential out-of-bounds shift 43d5ca88dfcd ALSA: usb-audio: Fix potential out-of-bounds shift
KCSAN: data-race in snd_rawmidi_poll / snd_rawmidi_proceed sound 378 1643d 1770d 19/28 1559d 88a06d6fd6b3 ALSA: rawmidi: Access runtime->avail always in spinlock
KMSAN: uninit-value in snd_seq_oss_synth_make_info (2) sound 1 1617d 1613d 19/28 1559d 217bfbb8b0bf ALSA: seq: oss: Fix missing error check in snd_seq_oss_synth_make_info()
UBSAN: shift-out-of-bounds in snd_pcm_oss_change_params_locked sound C unreliable 225 1635d 1650d 19/28 1559d 11cb881bf075 ALSA: pcm: oss: Fix a few more UBSAN fixes
KCSAN: data-race in snd_seq_check_queue / snd_seq_control_queue (3) sound 111 1644d 1789d 19/28 1559d 4ebd47037027 ALSA: seq: Use bool for snd_seq_queue internal flags
KASAN: use-after-free Read in snd_pcm_oss_release sound 1 1754d 1754d 15/28 1725d 77f4689de17c fix regression in "epoll: Keep a reference on files added to the check list"
WARNING in snd_pcm_plugin_build_mulaw sound C done 4 1752d 1749d 15/28 1725d 949a1ebe8cea ALSA: pcm: oss: Remove superfluous WARN_ON() for mulaw sanity check
general protection fault in snd_ctl_release sound syz done 4 1747d 1748d 15/28 1725d 77f4689de17c fix regression in "epoll: Keep a reference on files added to the check list"
KASAN: use-after-free Read in line6_submit_audio_in_all_urbs sound 2 1801d 1815d 15/28 1733d 68359a1ad844 ALSA: line6: Sync the pending work cancel at disconnection
KASAN: use-after-free Read in delete_and_unsubscribe_port (2) sound syz done 4 1777d 1803d 15/28 1733d 80982c7e834e ALSA: seq: oss: Serialize ioctls
WARNING in submit_audio_out_urb/usb_submit_urb sound usb syz 2 1803d 1803d 15/28 1733d 6e8a914ad619 ALSA: line6: Perform sanity check for each URB creation
KASAN: invalid-free in snd_seq_port_disconnect sound syz done 9 1777d 1782d 15/28 1733d 80982c7e834e ALSA: seq: oss: Serialize ioctls
WARNING in snd_info_get_line sound C done 36 1790d 1795d 15/28 1733d 60379ba08532 ALSA: info: Drop WARN_ON() from buffer NULL sanity check
KASAN: slab-out-of-bounds Write in snd_usb_mixer_notify_id usb sound C done 39 1813d 1818d 15/28 1794d 220345e98f1c ALSA: usb-audio: Fix OOB access of mixer element list
KASAN: slab-out-of-bounds Write in snd_usb_mixer_interrupt sound usb C done 5 1817d 1818d 15/28 1794d 220345e98f1c ALSA: usb-audio: Fix OOB access of mixer element list
linux-next test error: WARNING in snd_pcm_plug_alloc sound 3 1922d 1922d 15/28 1887d 5461e0530c22 ALSA: pcm: oss: Remove WARNING from snd_pcm_plug_alloc() checks
KCSAN: data-race in snd_seq_check_queue / snd_seq_control_queue sound 97 1888d 1986d 15/28 1887d bb51e669fa49 ALSA: seq: Avoid concurrent access to queue flags
KCSAN: data-race in queue_access_lock / snd_seq_check_queue sound 58 1927d 1969d 15/28 1887d bb51e669fa49 ALSA: seq: Avoid concurrent access to queue flags
KCSAN: data-race in __snd_rawmidi_transmit_ack / snd_rawmidi_write sound 168 1889d 2014d 15/28 1887d dfa9a5efe8b9 ALSA: rawmidi: Avoid bit fields for state flags
KASAN: slab-out-of-bounds Read in resample_shrink sound C done 5 1910d 1928d 15/28 1887d f2ecf903ef06 ALSA: pcm: oss: Avoid plugin buffer overflow
KCSAN: data-race in snd_seq_prioq_cell_out / snd_seq_timer_interrupt sound 118 1888d 1983d 15/28 1887d dc7497795e01 ALSA: seq: Fix concurrent access to queue current tick/time
memory leak in snd_pcm_hw_params sound C 25 1957d 1965d 15/28 1945d 66f2d19f8116 ALSA: pcm: Fix memory leak at closing a stream without hw_free
KASAN: use-after-free Read in snd_timer_resolution sound C 5 1961d 1978d 15/28 1945d 60adcfde92fa ALSA: seq: Fix racy access for queue timer in proc read
WARNING in azx_rirb_get_response sound 4 2007d 2009d 15/28 1949d 475feec0c41a ALSA: hda - Downgrade error message for single-cmd fallback
KASAN: slab-out-of-bounds Read in build_audio_procunit (2) sound usb C 1 2048d 2048d 15/28 1970d 976a68f06b2e ALSA: usb-audio: Fix incorrect size check for processing/extension units
KASAN: slab-out-of-bounds Read in linear_transfer (3) sound C done 5 2020d 2021d 15/28 1986d 4cc8d6505ab8 ALSA: pcm: oss: Avoid potential buffer overflows
KASAN: use-after-free Read in snd_timer_open sound C done 87 2043d 2044d 15/28 2012d 0c4f09ceec3d ALSA: timer: Fix the breakage of slave link open
general protection fault in snd_usb_create_mixer sound usb C 1 2035d 2034d 15/28 2012d 9435f2bb6687 ALSA: usb-audio: Fix NULL dereference at parsing BADD
KMSAN: use-after-free in build_audio_procunit usb sound C 2 2063d 2063d 14/28 2026d 976a68f06b2e ALSA: usb-audio: Fix incorrect size check for processing/extension units
KMSAN: uninit-value in get_min_max_with_quirks sound usb C 11 2058d 2047d 14/28 2026d 167beb175679 ALSA: usb-audio: Fix missing error check at mixer resolution test
KASAN: slab-out-of-bounds Read in build_audio_procunit usb sound C 6 2055d 2064d 13/28 2049d ba8bf0967a15 ALSA: usb-audio: Fix copy&paste error in the validator
KASAN: use-after-free Read in snd_seq_ioctl_get_client_pool sound 1 2127d 2125d 12/28 2109d 75545304eba6 ALSA: seq: Fix potential concurrent access to the deleted pool
INFO: task hung in snd_seq_write sound 6 2279d 2484d 12/28 2133d ede34f397ddb ALSA: seq: Break too long mutex context in the write loop
general protection fault in snd_usb_pipe_sanity_check usb sound C 72 2135d 2149d 12/28 2133d 5d78e1c2b7f4 ALSA: usb-audio: Fix gpf in snd_usb_pipe_sanity_check
INFO: rcu detected stall in snd_seq_write sound syz error 18 2154d 2484d 12/28 2133d ede34f397ddb ALSA: seq: Break too long mutex context in the write loop
KASAN: slab-out-of-bounds Read in linear_transfer (2) sound 1 2255d 2246d 12/28 2183d ca0214ee2802 ALSA: pcm: Fix possible OOB access in PCM oss plugins
KASAN: use-after-free Write in check_and_subscribe_port sound 1 2238d 2232d 12/28 2183d 7c32ae35fbf9 ALSA: seq: Cover unsubscribe_port() in list_mutex
WARNING: proc registration bug in snd_info_card_register usb sound C 453 2212d 2257d 12/28 2183d 0b074ab7fc0d ALSA: line6: Assure canceling delayed work at disconnection
KASAN: slab-out-of-bounds Write in default_read_copy_kernel sound C done 3 2304d 2380d 12/28 2183d ca0214ee2802 ALSA: pcm: Fix possible OOB access in PCM oss plugins
KASAN: null-ptr-deref Write in submit_audio_out_urb sound usb C 185 2196d 2212d 12/28 2189d 0b074ab7fc0d ALSA: line6: Assure canceling delayed work at disconnection
KASAN: use-after-free Read in snd_seq_timer_interrupt sound 1 2427d 2427d 12/28 2193d fe1b26c93d43 ALSA: timer: Make snd_timer_close() really kill pending actions
INFO: task hung in snd_seq_kernel_client_ctl sound C done 554 2257d 2258d 12/28 2193d f0654ba94e33 Revert "ALSA: seq: Protect in-kernel ioctl calls with mutex"
KASAN: use-after-free Read in snd_timer_process_callbacks sound C done 4 2259d 2260d 12/28 2193d df55531b8b0e ALSA: timer: Revert active callback sync check at close
KASAN: use-after-free Read in snd_seq_ioctl_get_subscription sound 2 2418d 2450d 12/28 2193d 2eabc5ec8ab4 ALSA: seq: Fix race of get-subscription call vs port-delete ioctls
BUG: sleeping function called from invalid context in line6_pcm_acquire sound 119 2212d 2231d 12/28 2193d 7f84ff68be05 ALSA: line6: toneport: Fix broken usage of timer for delayed execution
WARNING in port_delete sound syz done 22 2317d 2531d 12/28 2193d 7c32ae35fbf9 ALSA: seq: Cover unsubscribe_port() in list_mutex feb689025fbb ALSA: seq: Protect in-kernel ioctl calls with mutex
KASAN: use-after-free Read in snd_info_free_entry usb sound C 47 2224d 2254d 12/28 2212d 2a3f7221acdd ALSA: core: Fix card races between register and disconnect 8c2f870890fd ALSA: info: Fix racy addition/deletion of nodes
KASAN: slab-out-of-bounds Read in default_write_copy_kernel sound C done 366 2272d 2395d 12/28 2257d ca0214ee2802 ALSA: pcm: Fix possible OOB access in PCM oss plugins
INFO: rcu detected stall in snd_pcm_oss_read sound C 2 2366d 2366d 11/28 2294d e190161f96b8 ALSA: pcm: Fix tight loop of OSS capture stream
KASAN: use-after-free Read in snd_ctl_elem_add sound 1 2406d 2404d 11/28 2374d e1a7bfe38079 ALSA: control: Fix race between adding and removing a user element
KMSAN: uninit-value in linear_transfer (2) sound C 7 2388d 2411d 11/28 2383d 65766ee0bf7f ALSA: oss: Use kvzalloc() for local buffer allocations
KMSAN: uninit-value in snd_midi_event_encode_byte sound C 3 2478d 2478d 10/28 2454d 5a7b44a8df82 ALSA: rawmidi: Initialize allocated buffers
INFO: rcu detected stall in snd_pcm_oss_prepare sound 4 2624d 2626d 8/28 2476d e15dc99dbb9c ALSA: pcm: Fix endless loop for XRUN recovery in OSS emulation
BUG: soft lockup in snd_virmidi_output_trigger sound 3 2523d 2625d 8/28 2483d 50e9ffb1996a ALSA: virmidi: Fix too long output trigger loop
WARNING in __snd_rawmidi_transmit_ack (2) sound C 6 2490d 2498d 8/28 2483d 82fd4b05d704 ALSA: seq: virmidi: Fix discarding the unsubscribed output
WARNING in __snd_rawmidi_transmit_ack sound syz 2 2527d 2527d 8/28 2505d 39675f7a7c7e ALSA: rawmidi: Change resized buffers atomically
WARNING in __snd_pcm_lib_xfer sound syz 6 2600d 2602d 5/28 2587d f13876e2c33a ALSA: pcm: Check PCM state at xfern compat ioctl
BUG: unable to handle kernel paging request in memset_erms (2) sound C 11 2689d 2704d 5/28 2590d 02a5d6925cd3 ALSA: pcm: Avoid potential races between OSS ioctls and read/write
KASAN: null-ptr-deref Write in linear_transfer sound C 116 2636d 2719d 5/28 2591d 02a5d6925cd3 ALSA: pcm: Avoid potential races between OSS ioctls and read/write
BUG: unable to handle kernel paging request in snd_pcm_format_set_silence sound syz 11 2596d 2622d 5/28 2595d 02a5d6925cd3 ALSA: pcm: Avoid potential races between OSS ioctls and read/write
INFO: rcu detected stall in __snd_pcm_lib_xfer (2) sound C 1064 2623d 2628d 5/28 2595d e15dc99dbb9c ALSA: pcm: Fix endless loop for XRUN recovery in OSS emulation
WARNING in snd_pcm_hw_params sound C 56 2623d 2628d 5/28 2595d e1a3a981e320 ALSA: pcm: Remove WARN_ON() at snd_pcm_hw_params() error
INFO: rcu detected stall in io_playback_transfer sound 9 2623d 2628d 5/28 2595d e15dc99dbb9c ALSA: pcm: Fix endless loop for XRUN recovery in OSS emulation
general protection fault in snd_rawmidi_ioctl_compat sound 1 2623d 2615d 5/28 2595d 8a56ef4f3ffb ALSA: rawmidi: Fix missing input substream checks in compat ioctls
general protection fault in loopback_pos_update sound C 4 2704d 2701d 5/28 2595d 02a5d6925cd3 ALSA: pcm: Avoid potential races between OSS ioctls and read/write
KASAN: use-after-free Read in snd_pcm_timer_resolution sound C 3 2635d 2635d 5/28 2595d a820ccbe21e8 ALSA: pcm: Fix UAF at PCM release via PCM timer access
KASAN: use-after-free Read in snd_pcm_oss_get_formats sound C 3 2656d 2655d 4/28 2641d 01c0b4265cc1 ALSA: pcm: Fix UAF in snd_pcm_oss_get_formats()
INFO: rcu detected stall in memcpy sound 12 2716d 2720d 4/28 2678d 29159a4ed704 ALSA: pcm: Abort properly at pending signal in OSS read/write loops
BUG: looking up invalid subclass: 8 sound C 5 2779d 2778d 4/28 2692d 3510c7aa069a ALSA: seq: Avoid invalid lockdep class warning
WARNING in snd_interval_mulkdiv sound C 21 2707d 2713d 4/28 2702d 23b19b7b50fe ALSA: pcm: Remove yet superfluous WARN_ON()
INFO: task hung in snd_pcm_oss_write sound syz 2 2713d 2713d 3/28 2705d 29159a4ed704 ALSA: pcm: Abort properly at pending signal in OSS read/write loops
BUG: unable to handle kernel paging request in memset_erms sound C 35 2705d 2720d 3/28 2705d b088b53e20c7 ALSA: aloop: Fix inconsistent format due to incomplete rule
INFO: rcu detected stall in mulaw_transfer sound 37 2716d 2719d 3/28 2705d 898dfe4687f4 ALSA: aloop: Fix racy hw constraints adjustment
WARNING in snd_pcm_hw_param_first sound C 2905 2713d 2723d 3/28 2705d fe08f34d066f ALSA: pcm: Remove incorrect snd_BUG_ON() usages
suspicious RCU usage at sound/core/pcm_lib.c:LINE sound 1 2721d 2720d 3/28 2705d 29159a4ed704 ALSA: pcm: Abort properly at pending signal in OSS read/write loops
INFO: rcu detected stall in snd_pcm_plug_write_transfer sound 1 2714d 2714d 3/28 2705d 29159a4ed704 ALSA: pcm: Abort properly at pending signal in OSS read/write loops
BUG: soft lockup (2) sound C 29 2716d 2745d 3/28 2705d 29159a4ed704 ALSA: pcm: Abort properly at pending signal in OSS read/write loops
BUG: unable to handle kernel paging request in match_subs_info sound 1 2751d 2746d 3/28 2721d 7fb983b4dd56 x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu_tss
WARNING in initialize_timer sound 2 2754d 2755d 3/28 2734d 43a354287032 ALSA: seq: Remove spurious WARN_ON() at timer check
WARNING in snd_timer_user_info_compat sound C 174 2761d 2764d 3/28 2757d 3d4e8303f2c7 ALSA: timer: Remove kernel warning at compat ioctl error paths
KASAN: use-after-free Read in snd_timer_user_info_compat sound syz 2 2799d 2789d 3/28 2763d 79fb0518fec8 ALSA: timer: Add missing mutex lock for compat ioctls