======================================================
[ INFO: possible circular locking dependency detected ]
4.4.120-gd63fdf6 #28 Not tainted
-------------------------------------------------------
syz-executor0/6913 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-executor0/6913:
 #0:  (ashmem_mutex){+.+.+.}, at: [<ffffffff82c62016>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

stack backtrace:
CPU: 0 PID: 6913 Comm: syz-executor0 Not tainted 4.4.120-gd63fdf6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 da3c604ec1d9c547 ffff8801d88d7ad8 ffffffff81d0408d
 ffffffff851a0010 ffffffff851a9d00 ffffffff851be610 ffff8801d89088f8
 ffff8801d8908000 ffff8801d88d7b20 ffffffff81233ba1 ffff8801d89088f8
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: 6946:6947 IncRefs 0 refcount change on invalid ref 1 ret -22
binder: BINDER_SET_CONTEXT_MGR already set
binder: 6946:6947 ioctl 40046207 0 returned -16
binder: 6946:6956 IncRefs 0 refcount change on invalid ref 1 ret -22
binder: 6969:6973 got transaction to invalid handle
binder: 6969:6973 transaction failed 29201/-22, size 32-0 line 3005
binder: 6974:6977 unknown command 1021178515
binder: undelivered TRANSACTION_ERROR: 29201
binder: 6974:6977 ioctl c0306201 20008000 returned -22
binder: 6974:6987 unknown command 1021178515
binder: 6974:6987 ioctl c0306201 20008000 returned -22
binder: 6993:7003 unknown command 1021178515
binder: 6993:7003 ioctl c0306201 20008000 returned -22
netlink: 4 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 4 bytes leftover after parsing attributes in process `syz-executor1'.
binder: 7035:7039 unknown command 1021178515
binder: 7035:7039 ioctl c0306201 20008000 returned -22
binder: 7052:7059 unknown command 1021178515
binder: 7052:7059 ioctl c0306201 20008000 returned -22
device bridge0 entered promiscuous mode
binder: 7083:7086 unknown command 1021178515
binder: 7083:7086 ioctl c0306201 20008000 returned -22
binder: 7099:7101 unknown command 1021178515
binder: 7099:7101 ioctl c0306201 20008000 returned -22
binder: 7103:7106 unknown command 1021178515
binder: 7103:7106 ioctl c0306201 20008000 returned -22
netlink: 4 bytes leftover after parsing attributes in process `syz-executor7'.
audit: type=1400 audit(1521751739.561:19): avc:  denied  { create } for  pid=7191 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_fib_lookup_socket permissive=1
netlink: 4 bytes leftover after parsing attributes in process `syz-executor7'.
audit: type=1400 audit(1521751739.601:20): avc:  denied  { getattr } for  pid=7191 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_fib_lookup_socket permissive=1
audit: type=1400 audit(1521751739.631:21): avc:  denied  { write } for  pid=7191 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_fib_lookup_socket permissive=1
binder: 7276:7284 transaction failed 29201/-28, size 0-0 line 3128
binder: BINDER_SET_CONTEXT_MGR already set
binder: 7276:7297 ioctl 40046207 0 returned -16
binder_alloc: 7276: binder_alloc_buf, no vma
binder: 7276:7297 transaction failed 29189/-3, size 0-0 line 3128
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29201
netlink: 4 bytes leftover after parsing attributes in process `syz-executor5'.
BUG: using __this_cpu_add() in preemptible [00000000] code: syz-executor5/7867
caller is __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
CPU: 1 PID: 7867 Comm: syz-executor5 Not tainted 4.4.120-gd63fdf6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 92283826ac67242c ffff8801d29b7638 ffffffff81d0408d
 0000000000000001 ffffffff839fe5a0 ffffffff83cefc20 ffff8800b62f4800
 0000000000000003 ffff8801d29b7678 ffffffff81d63fe4 ffff8801d6781e88
Call Trace:
 [<ffffffff81d0408d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0408d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81d63fe4>] check_preemption_disabled+0x1d4/0x200 lib/smp_processor_id.c:46
 [<ffffffff81d6404c>] __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
 [<ffffffff8312b439>] tcp_try_coalesce+0x249/0x4d0 net/ipv4/tcp_input.c:4278
 [<ffffffff831335b7>] tcp_queue_rcv+0x127/0x720 net/ipv4/tcp_input.c:4485
 [<ffffffff8314ae8b>] tcp_send_rcvq+0x39b/0x450 net/ipv4/tcp_input.c:4531
 [<ffffffff831220ef>] tcp_sendmsg+0x1e8f/0x2b10 net/ipv4/tcp.c:1134
 [<ffffffff831d7d4c>] inet_sendmsg+0x2bc/0x4c0 net/ipv4/af_inet.c:755
 [<ffffffff82deba6a>] sock_sendmsg_nosec net/socket.c:625 [inline]
 [<ffffffff82deba6a>] sock_sendmsg+0xca/0x110 net/socket.c:635
 [<ffffffff82debcd6>] sock_write_iter+0x226/0x3b0 net/socket.c:834
 [<ffffffff8151e0b8>] do_iter_readv_writev+0x138/0x1e0 fs/read_write.c:664
 [<ffffffff8151f852>] do_readv_writev+0x2d2/0x6e0 fs/read_write.c:808
 [<ffffffff8151fd8b>] vfs_writev+0x7b/0xb0 fs/read_write.c:847
 [<ffffffff81522249>] SYSC_writev fs/read_write.c:880 [inline]
 [<ffffffff81522249>] SyS_writev+0xd9/0x240 fs/read_write.c:872
 [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98
BUG: using __this_cpu_add() in preemptible [00000000] code: syz-executor5/7887
caller is __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
CPU: 1 PID: 7887 Comm: syz-executor5 Not tainted 4.4.120-gd63fdf6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 9e11fa5b9c160da7 ffff8800b94b7638 ffffffff81d0408d
 0000000000000001 ffffffff839fe5a0 ffffffff83cefc20 ffff8801d2a20000
 0000000000000003 ffff8800b94b7678 ffffffff81d63fe4 ffff8801d2ccd348
Call Trace:
 [<ffffffff81d0408d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0408d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81d63fe4>] check_preemption_disabled+0x1d4/0x200 lib/smp_processor_id.c:46
 [<ffffffff81d6404c>] __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
 [<ffffffff8312b439>] tcp_try_coalesce+0x249/0x4d0 net/ipv4/tcp_input.c:4278
 [<ffffffff831335b7>] tcp_queue_rcv+0x127/0x720 net/ipv4/tcp_input.c:4485
 [<ffffffff8314ae8b>] tcp_send_rcvq+0x39b/0x450 net/ipv4/tcp_input.c:4531
 [<ffffffff831220ef>] tcp_sendmsg+0x1e8f/0x2b10 net/ipv4/tcp.c:1134
 [<ffffffff831d7d4c>] inet_sendmsg+0x2bc/0x4c0 net/ipv4/af_inet.c:755
 [<ffffffff82deba6a>] sock_sendmsg_nosec net/socket.c:625 [inline]
 [<ffffffff82deba6a>] sock_sendmsg+0xca/0x110 net/socket.c:635
 [<ffffffff82debcd6>] sock_write_iter+0x226/0x3b0 net/socket.c:834
 [<ffffffff8151e0b8>] do_iter_readv_writev+0x138/0x1e0 fs/read_write.c:664
 [<ffffffff8151f852>] do_readv_writev+0x2d2/0x6e0 fs/read_write.c:808
 [<ffffffff8151fd8b>] vfs_writev+0x7b/0xb0 fs/read_write.c:847
 [<ffffffff81522249>] SYSC_writev fs/read_write.c:880 [inline]
 [<ffffffff81522249>] SyS_writev+0xd9/0x240 fs/read_write.c:872
 [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
SELinux:  policydb magic number 0x2d14d9e7 does not match expected magic number 0xf97cff8c
SELinux:  policydb magic number 0x2d14d9e7 does not match expected magic number 0xf97cff8c
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=4439 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=4439 sclass=netlink_route_socket
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 44 bytes leftover after parsing attributes in process `syz-executor0'.
binder: 9208:9212 ioctl 4b3b 200001c0 returned -22
binder: 9208:9212 ioctl 4b3b 200001c0 returned -22