On Sat, Jan 30, 2016 at 9:28 PM, Dmitry Vyukov dvyukov@google.com wrote:
Hello,
I've got the following deadlock report while running syzkaller fuzzer:
[ INFO: possible circular locking dependency detected ] 4.5.0-rc1+ #305 Not tainted
syz-executor/14254 is trying to acquire lock: (&runtime->oss.params_lock){+.+.+.}, at: [<ffffffff8528a504>] snd_pcm_oss_change_params+0xd4/0x3540 sound/core/oss/pcm_oss.c:852
but task is already holding lock: (&mm->mmap_sem){++++++}, at: [<ffffffff816b267c>] vm_mmap_pgoff
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mm->mmap_sem){++++++}: [<ffffffff8145b9dc>] lock_acquire+0x1dc/0x430 kernel/locking/lockdep.c:3587 [<ffffffff816def51>] __might_fault+0x141/0x1d0 mm/memory.c:3802 [< inline >] copy_from_user ./arch/x86/include/asm/uaccess.h:714 [< inline >] snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1376 [<ffffffff852940f0>] snd_pcm_oss_write+0x250/0x700 sound/core/oss/pcm_oss.c:2694 [<ffffffff817b90b3>] __vfs_write+0x113/0x480 fs/read_write.c:528 [<ffffffff817bab47>] vfs_write+0x167/0x4a0 fs/read_write.c:577 [< inline >] SYSC_write fs/read_write.c:624 [<ffffffff817bde31>] SyS_write+0x111/0x220 fs/read_write.c:616 [<ffffffff866531b6>] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185
-> #0 (&runtime->oss.params_lock){+.+.+.}: [< inline >] check_prev_add kernel/locking/lockdep.c:1855 [< inline >] check_prevs_add kernel/locking/lockdep.c:1960 [< inline >] validate_chain kernel/locking/lockdep.c:2146 [<ffffffff8145807b>] __lock_acquire+0x31eb/0x4700 kernel/locking/lockdep.c:3208 [<ffffffff8145b9dc>] lock_acquire+0x1dc/0x430 kernel/locking/lockdep.c:3587 [< inline >] __mutex_lock_common kernel/locking/mutex.c:518 [<ffffffff8664891c>] mutex_lock_interruptible_nested+0xbc/0xbe0 kernel/locking/mutex.c:647 [<ffffffff8528a504>] snd_pcm_oss_change_params+0xd4/0x3540 sound/core/oss/pcm_oss.c:852 [<ffffffff8528f01d>] snd_pcm_oss_mmap+0x3dd/0x4c0 sound/core/oss/pcm_oss.c:2807 [<ffffffff81705747>] mmap_region+0x897/0x1010 mm/mmap.c:1624 [<ffffffff81706614>] do_mmap+0x754/0x990 mm/mmap.c:1403 [< inline >] do_mmap_pgoff include/linux/mm.h:1982 [<ffffffff816b26af>] vm_mmap_pgoff+0x15f/0x1b0 mm/util.c:328 [< inline >] SYSC_mmap_pgoff mm/mmap.c:1453 [<ffffffff816ff85a>] SyS_mmap_pgoff+0x34a/0x580 mm/mmap.c:1411 [< inline >] SYSC_mmap arch/x86/kernel/sys_x86_64.c:95 [<ffffffff811aeeb6>] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:86 [<ffffffff866531b6>] entry_SYSCALL_64_fastpath+0x16/0x7a arch/x86/entry/entry_64.S:185
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ----lock(&mm->mmap_sem); lock(&runtime->oss.params_lock); lock(&mm->mmap_sem); lock(&runtime->oss.params_lock);
*** DEADLOCK ***
1 lock held by syz-executor/14254: #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816b267c>] vm_mmap_pgoff+0x12c/0x1b0 mm/util.c:327
stack backtrace: CPU: 2 PID: 14254 Comm: syz-executor Not tainted 4.5.0-rc1+ #305 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 00000000ffffffff ffff88003214f780 ffffffff82be11ad ffffffff8959ac60 ffffffff8959ac60 ffffffff89573f60 ffff88003214f7d0 ffffffff814512a8 ffff8800333cdf00 ffff8800333ce742 0000000000000000 ffff8800333ce720 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff82be11ad>] dump_stack+0x6f/0xa2 lib/dump_stack.c:50 [<ffffffff814512a8>] print_circular_bug+0x288/0x340 kernel/locking/lockdep.c:1228 [< inline >] check_prev_add kernel/locking/lockdep.c:1855 [< inline >] check_prevs_add kernel/locking/lockdep.c:1960 [< inline >] validate_chain kernel/locking/lockdep.c:2146 [<ffffffff8145807b>] __lock_acquire+0x31eb/0x4700 kernel/locking/lockdep.c:3208 [<ffffffff8145b9dc>] lock_acquire+0x1dc/0x430 kernel/locking/lockdep.c:3587 [< inline >] __mutex_lock_common kernel/locking/mutex.c:518 [<ffffffff8664891c>] mutex_lock_interruptible_nested+0xbc/0xbe0 kernel/locking/mutex.c:647 [<ffffffff8528a504>] snd_pcm_oss_change_params+0xd4/0x3540 sound/core/oss/pcm_oss.c:852 [<ffffffff8528f01d>] snd_pcm_oss_mmap+0x3dd/0x4c0 sound/core/oss/pcm_oss.c:2807 [<ffffffff81705747>] mmap_region+0x897/0x1010 mm/mmap.c:1624 [<ffffffff81706614>] do_mmap+0x754/0x990 mm/mmap.c:1403 [< inline >] do_mmap_pgoff include/linux/mm.h:1982 [<ffffffff816b26af>] vm_mmap_pgoff+0x15f/0x1b0 mm/util.c:328 [< inline >] SYSC_mmap_pgoff mm/mmap.c:1453 [<ffffffff816ff85a>] SyS_mmap_pgoff+0x34a/0x580 mm/mmap.c:1411 [< inline >] SYSC_mmap arch/x86/kernel/sys_x86_64.c:95 [<ffffffff811aeeb6>] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:86
On commit 26cd83670f2f5a3d5b5514a1f7d96567cdb9558b.
Similar for snd_pcm_oss_read:
[ 90.050883] [ INFO: possible circular locking dependency detected ] [ 90.050883] 4.5.0-rc1+ #305 Not tainted [ 90.050883] ------------------------------------------------------- [ 90.050883] syz-executor/11689 is trying to acquire lock: [ 90.050883] (&runtime->oss.params_lock){+.+.+.}, at: [<ffffffff8528a504>] snd_pcm_oss_change_params+0xd4/0x3540 [ 90.050883] [ 90.050883] but task is already holding lock: [ 90.050883] (&mm->mmap_sem){++++++}, at: [<ffffffff816b267c>] vm_mmap_pgoff+0x12c/0x1b0 [ 90.050883] [ 90.050883] which lock already depends on the new lock. [ 90.050883] [ 90.050883] [ 90.050883] the existing dependency chain (in reverse order) is: [ 90.050883] -> #1 (&mm->mmap_sem){++++++}: [ 90.050883] [<ffffffff8145b9dc>] lock_acquire+0x1dc/0x430 [ 90.050883] [<ffffffff816def51>] __might_fault+0x141/0x1d0 [ 90.050883] [<ffffffff85295062>] snd_pcm_oss_read+0x262/0x560 [ 90.050883] [<ffffffff817b7183>] __vfs_read+0x113/0x460 [ 90.050883] [<ffffffff817ba7d6>] vfs_read+0x106/0x310 [ 90.050883] [<ffffffff817bdc11>] SyS_read+0x111/0x220 [ 90.050883] [<ffffffff866531b6>] entry_SYSCALL_64_fastpath+0x16/0x7a [ 90.050883] -> #0 (&runtime->oss.params_lock){+.+.+.}: [ 90.050883] [<ffffffff8145807b>] __lock_acquire+0x31eb/0x4700 [ 90.050883] [<ffffffff8145b9dc>] lock_acquire+0x1dc/0x430 [ 90.050883] [<ffffffff8664891c>] mutex_lock_interruptible_nested+0xbc/0xbe0 [ 90.050883] [<ffffffff8528a504>] snd_pcm_oss_change_params+0xd4/0x3540 [ 90.050883] [<ffffffff8528f01d>] snd_pcm_oss_mmap+0x3dd/0x4c0 [ 90.050883] [<ffffffff81705747>] mmap_region+0x897/0x1010 [ 90.050883] [<ffffffff81706614>] do_mmap+0x754/0x990 [ 90.050883] [<ffffffff816b26af>] vm_mmap_pgoff+0x15f/0x1b0 [ 90.050883] [<ffffffff816ff85a>] SyS_mmap_pgoff+0x34a/0x580 [ 90.050883] [<ffffffff811aeeb6>] SyS_mmap+0x16/0x20 [ 90.050883] [<ffffffff866531b6>] entry_SYSCALL_64_fastpath+0x16/0x7a