======================================================
[ INFO: possible circular locking dependency detected ]
4.4.120-gd63fdf6 #28 Not tainted
-------------------------------------------------------
syz-executor2/12511 is trying to acquire lock:
 (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<ffffffff81463361>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816

but task is already holding lock:
 (ashmem_mutex){+.+.+.}, at: [<ffffffff82c62016>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff8123d7ce>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
       [<ffffffff8376a39b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8376a39b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
       [<ffffffff82c61463>] ashmem_mmap+0x53/0x400 drivers/staging/android/ashmem.c:366
       [<ffffffff814b0e4f>] mmap_region+0x94f/0x1250 mm/mmap.c:1664
       [<ffffffff814b1c4d>] do_mmap+0x4fd/0x9d0 mm/mmap.c:1441
       [<ffffffff814700ce>] do_mmap_pgoff include/linux/mm.h:1915 [inline]
       [<ffffffff814700ce>] vm_mmap_pgoff+0x16e/0x1c0 mm/util.c:296
       [<ffffffff814afe1f>] SYSC_mmap_pgoff mm/mmap.c:1491 [inline]
       [<ffffffff814afe1f>] SyS_mmap_pgoff+0x33f/0x560 mm/mmap.c:1449
       [<ffffffff8101beb6>] SYSC_mmap arch/x86/kernel/sys_x86_64.c:95 [inline]
       [<ffffffff8101beb6>] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:86
       [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98

       [<ffffffff8123d7ce>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
       [<ffffffff814956ea>] __might_fault+0x14a/0x1d0 mm/memory.c:3810
       [<ffffffff8155ab22>] copy_to_user arch/x86/include/asm/uaccess.h:760 [inline]
       [<ffffffff8155ab22>] filldir+0x162/0x2d0 fs/readdir.c:180
       [<ffffffff8159820e>] dir_emit_dot include/linux/fs.h:3070 [inline]
       [<ffffffff8159820e>] dir_emit_dots include/linux/fs.h:3081 [inline]
       [<ffffffff8159820e>] dcache_readdir+0x11e/0x7b0 fs/libfs.c:150
       [<ffffffff8155a768>] iterate_dir+0x1c8/0x420 fs/readdir.c:42
       [<ffffffff8155b45a>] SYSC_getdents fs/readdir.c:215 [inline]
       [<ffffffff8155b45a>] SyS_getdents+0x14a/0x270 fs/readdir.c:196
       [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98

       [<ffffffff8123ab2f>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff8123ab2f>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff8123ab2f>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff8123ab2f>] __lock_acquire+0x371f/0x4b50 kernel/locking/lockdep.c:3213
       [<ffffffff8123d7ce>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
       [<ffffffff8376a39b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8376a39b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
       [<ffffffff81463361>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
       [<ffffffff8151c762>] vfs_llseek+0xa2/0xd0 fs/read_write.c:260
       [<ffffffff82c620a7>] ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:342
       [<ffffffff8151e56b>] vfs_llseek fs/read_write.c:260 [inline]
       [<ffffffff8151e56b>] SYSC_lseek fs/read_write.c:285 [inline]
       [<ffffffff8151e56b>] SyS_lseek+0xeb/0x170 fs/read_write.c:276
       [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98

other info that might help us debug this:

Chain exists of:
 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(ashmem_mutex);
                               lock(&mm->mmap_sem);
                               lock(ashmem_mutex);
  lock(&sb->s_type->i_mutex_key#10);

 *** DEADLOCK ***

1 lock held by syz-executor2/12511:
 #0:  (ashmem_mutex){+.+.+.}, at: [<ffffffff82c62016>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

stack backtrace:
CPU: 1 PID: 12511 Comm: syz-executor2 Not tainted 4.4.120-gd63fdf6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 c8fc55a50c2b5f3f ffff8801d26e7ad8 ffffffff81d0408d
 ffffffff851a0010 ffffffff851a9d00 ffffffff851be970 ffff8801cf72a0f8
 ffff8801cf729800 ffff8801d26e7b20 ffffffff81233ba1 ffff8801cf72a0f8
Call Trace:
 [<ffffffff81d0408d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0408d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81233ba1>] print_circular_bug+0x271/0x310 kernel/locking/lockdep.c:1226
 [<ffffffff8123ab2f>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff8123ab2f>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff8123ab2f>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff8123ab2f>] __lock_acquire+0x371f/0x4b50 kernel/locking/lockdep.c:3213
 [<ffffffff8123d7ce>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
 [<ffffffff8376a39b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff8376a39b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
 [<ffffffff81463361>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
 [<ffffffff8151c762>] vfs_llseek+0xa2/0xd0 fs/read_write.c:260
 [<ffffffff82c620a7>] ashmem_llseek+0xe7/0x1f0 drivers/staging/android/ashmem.c:342
 [<ffffffff8151e56b>] vfs_llseek fs/read_write.c:260 [inline]
 [<ffffffff8151e56b>] SYSC_lseek fs/read_write.c:285 [inline]
 [<ffffffff8151e56b>] SyS_lseek+0xeb/0x170 fs/read_write.c:276
 [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98
binder: 12548:12549 got transaction with invalid offsets ptr
binder: 12548:12549 transaction failed 29201/-14, size 40-8 line 3156
binder: BINDER_SET_CONTEXT_MGR already set
binder: 12548:12553 ioctl 40046207 0 returned -16
binder_alloc: 12548: binder_alloc_buf, no vma
binder: 12548:12549 transaction failed 29189/-3, size 40-8 line 3128
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29201
SELinux:  policydb magic number 0x0 does not match expected magic number 0xf97cff8c
SELinux:  policydb magic number 0x0 does not match expected magic number 0xf97cff8c
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
binder: 12829:12831 BC_DEAD_BINDER_DONE 0000000000000000 not found
binder: 12829:12843 BC_DEAD_BINDER_DONE 0000000000000000 not found
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
audit: type=1400 audit(1521670841.278:40): avc:  denied  { set_context_mgr } for  pid=12957 comm="syz-executor2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=binder permissive=1
audit: type=1400 audit(1521670841.318:41): avc:  denied  { call } for  pid=12957 comm="syz-executor2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=binder permissive=1
binder: release 12957:12959 transaction 84 out, still active
binder: undelivered TRANSACTION_COMPLETE
binder: BINDER_SET_CONTEXT_MGR already set
binder: 12957:12965 ioctl 40046207 0 returned -16
binder_alloc: 12957: binder_alloc_buf, no vma
binder: 12957:12965 transaction failed 29189/-3, size 0-0 line 3128
binder: undelivered TRANSACTION_ERROR: 29189
binder: send failed reply for transaction 84, target dead
audit: type=1400 audit(1521670841.558:42): avc:  denied  { set_context_mgr } for  pid=13028 comm="syz-executor5" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=binder permissive=1
binder: 13028:13038 ioctl c0306201 20007000 returned -14
binder: 13028:13045 ioctl c0306201 20004000 returned -14
binder_alloc: binder_alloc_mmap_handler: 13028 20000000-20002000 already mapped failed -16
binder: BINDER_SET_CONTEXT_MGR already set
binder: 13028:13053 ioctl c0306201 20007000 returned -14
binder: 13028:13045 ioctl 40046207 0 returned -16
audit: type=1400 audit(1521670841.728:43): avc:  denied  { create } for  pid=13067 comm="syz-executor0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1521670841.768:44): avc:  denied  { write } for  pid=13067 comm="syz-executor0" path="socket:[28730]" dev="sockfs" ino=28730 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1521670842.498:45): avc:  denied  { create } for  pid=13188 comm="syz-executor1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
audit: type=1400 audit(1521670842.528:46): avc:  denied  { setopt } for  pid=13191 comm="syz-executor0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
sg_write: data in/out 167162/1 bytes for SCSI command 0x67-- guessing data in;
   program syz-executor2 not setting count and/or reply_len properly
netlink: 8 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor3'.
audit: type=1400 audit(1521670843.118:47): avc:  denied  { create } for  pid=13335 comm="syz-executor3" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_crypto_socket permissive=1