======================================================
[ INFO: possible circular locking dependency detected ]
4.4.120-gd63fdf6 #28 Not tainted
-------------------------------------------------------
syz-executor7/6532 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-executor7/6532:
 #0:  (ashmem_mutex){+.+.+.}, at: [<ffffffff82c62016>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

stack backtrace:
CPU: 1 PID: 6532 Comm: syz-executor7 Not tainted 4.4.120-gd63fdf6 #28
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 d0e05e4ac0b233eb ffff8801d713fad8 ffffffff81d0408d
 ffffffff851a0010 ffffffff851a9d00 ffffffff851be7c0 ffff8801d7a468f8
 ffff8801d7a46000 ffff8801d713fb20 ffffffff81233ba1 ffff8801d7a468f8
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
audit: type=1400 audit(1521832097.767:22): avc:  denied  { create } for  pid=6548 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_scsitransport_socket permissive=1
binder: binder_mmap: 6573 20000000-20003000 bad vm_flags failed -1
rfkill: input handler disabled
rfkill: input handler enabled
binder: binder_mmap: 6573 20000000-20003000 bad vm_flags failed -1
audit: type=1400 audit(1521832097.927:23): avc:  denied  { bind } for  pid=6601 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=netlink_generic_socket permissive=1
audit: type=1400 audit(1521832098.467:24): avc:  denied  { read } for  pid=6649 comm="syz-executor1" path="socket:[15111]" dev="sockfs" ino=15111 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
sock: process `syz-executor4' is using obsolete setsockopt SO_BSDCOMPAT
audit: type=1326 audit(1521832098.907:25): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=6801 comm="syz-executor7" exe="/root/syz-executor7" sig=31 arch=c000003e syscall=202 compat=0 ip=0x454239 code=0x0
audit: type=1326 audit(1521832098.937:26): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=6801 comm="syz-executor7" exe="/root/syz-executor7" sig=31 arch=c000003e syscall=202 compat=0 ip=0x454239 code=0x0
binder_alloc: binder_alloc_mmap_handler: 6830 20000000-20002000 already mapped failed -16
binder: BINDER_SET_CONTEXT_MGR already set
binder: 6830:6833 ioctl 40046207 0 returned -16
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
binder_alloc: 6830: binder_alloc_buf, no vma
binder: 6830:6833 transaction failed 29189/-3, size 0-0 line 3128
binder: undelivered TRANSACTION_ERROR: 29189
binder: release 6830:6833 transaction 12 out, still active
binder: undelivered TRANSACTION_COMPLETE
binder: send failed reply for transaction 12, target dead
IPVS: Creating netns size=2552 id=9
netlink: 8 bytes leftover after parsing attributes in process `syz-executor0'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor0'.
pktgen: kernel_thread() failed for cpu 0
pktgen: Cannot create thread for cpu 0 (-4)
pktgen: kernel_thread() failed for cpu 1
pktgen: Cannot create thread for cpu 1 (-4)
pktgen: Initialization failed for all threads
BUG: using __this_cpu_read() in preemptible [00000000] code: syz-executor0/7078
caller is __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
CPU: 1 PID: 7078 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 0e6fba94b861b01e ffff8800b75c76b8 ffffffff81d0408d
 0000000000000001 ffffffff839fe5a0 ffffffff83d0be20 ffff8801d6a9b000
 0000000000000003 ffff8800b75c76f8 ffffffff81d63fe4 ffff8800b75c7710
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
 [<ffffffff832e2f08>] ipcomp_alloc_tfms net/xfrm/xfrm_ipcomp.c:286 [inline]
 [<ffffffff832e2f08>] ipcomp_init_state+0x188/0x980 net/xfrm/xfrm_ipcomp.c:363
 [<ffffffff833eb945>] ipcomp6_init_state+0xb5/0x820 net/ipv6/ipcomp6.c:165
 [<ffffffff832c1817>] __xfrm_init_state+0x3e7/0xb30 net/xfrm/xfrm_state.c:2058
 [<ffffffff832c1f7a>] xfrm_init_state+0x1a/0x20 net/xfrm/xfrm_state.c:2084
 [<ffffffff8344681b>] pfkey_msg2xfrm_state net/key/af_key.c:1289 [inline]
 [<ffffffff8344681b>] pfkey_add+0x1fbb/0x3490 net/key/af_key.c:1506
 [<ffffffff8344a45b>] pfkey_process+0x68b/0x750 net/key/af_key.c:2834
 [<ffffffff8344bcb9>] pfkey_sendmsg+0x3a9/0x760 net/key/af_key.c:3678
 [<ffffffff82deba6a>] sock_sendmsg_nosec net/socket.c:625 [inline]
 [<ffffffff82deba6a>] sock_sendmsg+0xca/0x110 net/socket.c:635
 [<ffffffff82ded641>] ___sys_sendmsg+0x6c1/0x7c0 net/socket.c:1962
 [<ffffffff82def693>] __sys_sendmsg+0xd3/0x190 net/socket.c:1996
 [<ffffffff82def77d>] SYSC_sendmsg net/socket.c:2007 [inline]
 [<ffffffff82def77d>] SyS_sendmsg+0x2d/0x50 net/socket.c:2003
 [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98
audit: type=1400 audit(1521832100.827:27): avc:  denied  { getopt } for  pid=7251 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_netfilter_socket permissive=1
audit: type=1400 audit(1521832100.857:28): avc:  denied  { lock } for  pid=7251 comm="syz-executor3" path="socket:[16119]" dev="sockfs" ino=16119 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
pktgen: kernel_thread() failed for cpu 0
pktgen: Cannot create thread for cpu 0 (-4)
pktgen: kernel_thread() failed for cpu 1
pktgen: Cannot create thread for cpu 1 (-4)
pktgen: Initialization failed for all threads
pktgen: kernel_thread() failed for cpu 0
pktgen: Cannot create thread for cpu 0 (-4)
pktgen: kernel_thread() failed for cpu 1
pktgen: Cannot create thread for cpu 1 (-4)
pktgen: Initialization failed for all threads
keychord: Insufficient bytes present for keycount 3
keychord: Insufficient bytes present for keycount 3
binder: 7400:7413 got transaction with invalid data ptr
audit: type=1400 audit(1521832101.997:29): avc:  denied  { create } for  pid=7401 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_iscsi_socket permissive=1
binder: 7400:7413 transaction failed 29201/-14, size 40-8 line 3147
binder: BINDER_SET_CONTEXT_MGR already set
binder: 7400:7425 ioctl 40046207 0 returned -16
binder_alloc: 7400: binder_alloc_buf, no vma
binder: 7400:7413 transaction failed 29189/-3, size 40-8 line 3128
binder: 7400:7425 BC_CLEAR_DEATH_NOTIFICATION invalid ref 0
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29201
ALSA: seq fatal error: cannot create timer (-22)
ALSA: seq fatal error: cannot create timer (-22)
IPVS: Creating netns size=2552 id=10
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
audit: type=1400 audit(1521832104.097:30): avc:  denied  { create } for  pid=7734 comm="syz-executor4" 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
syz-executor6 uses obsolete (PF_INET,SOCK_PACKET)
mmap: syz-executor1 (8069) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.txt.
IPv4: Oversized IP packet from 127.0.0.1
IPv4: Oversized IP packet from 127.0.0.1
device bridge0 entered promiscuous mode
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=60189 sclass=netlink_xfrm_socket
SELinux: unrecognized netlink message: protocol=6 nlmsg_type=60189 sclass=netlink_xfrm_socket
binder: 8299:8302 unknown command 208797696
binder: 8299:8302 ioctl c0306201 20000040 returned -22
binder: BINDER_SET_CONTEXT_MGR already set
binder: 8299:8302 ioctl 40046207 0 returned -16
binder: 8299:8311 unknown command 208797696
binder: 8299:8311 ioctl c0306201 20000040 returned -22
keychord: keycode 9294 out of range
binder: 8449:8465 unknown command -243877473
binder: 8449:8465 ioctl c0306201 20007000 returned -22
IPv4: Oversized IP packet from 127.0.0.1
audit: type=1400 audit(1521832106.557:31): avc:  denied  { dyntransition } for  pid=8511 comm="syz-executor3" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0 tclass=process permissive=1
IPv4: Oversized IP packet from 127.0.0.1
netlink: 20 bytes leftover after parsing attributes in process `syz-executor1'.
BUG: using __this_cpu_read() in preemptible [00000000] code: syz-executor5/8643
caller is __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
CPU: 0 PID: 8643 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 4c2e090f57f595c2 ffff8801c6c8f6c8 ffffffff81d0408d
 0000000000000000 ffffffff839fe5a0 ffffffff83d0be20 ffff8801d0ef1800
 0000000000000003 ffff8801c6c8f708 ffffffff81d63fe4 ffff8801c6c8f720
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
 [<ffffffff832e2f08>] ipcomp_alloc_tfms net/xfrm/xfrm_ipcomp.c:286 [inline]
 [<ffffffff832e2f08>] ipcomp_init_state+0x188/0x980 net/xfrm/xfrm_ipcomp.c:363
 [<ffffffff8324ac70>] ipcomp4_init_state+0xb0/0x7d0 net/ipv4/ipcomp.c:137
 [<ffffffff832c1817>] __xfrm_init_state+0x3e7/0xb30 net/xfrm/xfrm_state.c:2058
 [<ffffffff832c1f7a>] xfrm_init_state+0x1a/0x20 net/xfrm/xfrm_state.c:2084
 [<ffffffff8344681b>] pfkey_msg2xfrm_state net/key/af_key.c:1289 [inline]
 [<ffffffff8344681b>] pfkey_add+0x1fbb/0x3490 net/key/af_key.c:1506
 [<ffffffff8344a45b>] pfkey_process+0x68b/0x750 net/key/af_key.c:2834
 [<ffffffff8344bcb9>] pfkey_sendmsg+0x3a9/0x760 net/key/af_key.c:3678
 [<ffffffff82deba6a>] sock_sendmsg_nosec net/socket.c:625 [inline]
 [<ffffffff82deba6a>] sock_sendmsg+0xca/0x110 net/socket.c:635
 [<ffffffff82ded641>] ___sys_sendmsg+0x6c1/0x7c0 net/socket.c:1962
 [<ffffffff82def693>] __sys_sendmsg+0xd3/0x190 net/socket.c:1996
 [<ffffffff82def77d>] SYSC_sendmsg net/socket.c:2007 [inline]
 [<ffffffff82def77d>] SyS_sendmsg+0x2d/0x50 net/socket.c:2003
 [<ffffffff8377395f>] entry_SYSCALL_64_fastpath+0x1c/0x98
BUG: using __this_cpu_read() in preemptible [00000000] code: syz-executor5/8643
caller is __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62
CPU: 0 PID: 8643 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 4c2e090f57f595c2 ffff8801c6c8f6c8 ffffffff81d0408d
 0000000000000000 ffffffff839fe5a0 ffffffff83d0be20 ffff8801d0ef1800
 0000000000000003 ffff8801c6c8f708 ffffffff81d63fe4 ffff8801c6c8f720
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
 [<ffffffff832e2f08>] ipcomp_alloc_tfms net/xfrm/xfrm_ipcomp.c:286 [inline]
 [<ffffffff832e2f08>] ipcomp_init_state+0x188/0x980 net/xfrm/xfrm_ipcomp.c:363
 [<ffffffff8324ac70>] ipcomp4_init_state+0xb0/0x7d0 net/ipv4/ipcomp.c:137
 [<ffffffff832c1817>] __xfrm_init_state+0x3e7/0xb30 net/xfrm/xfrm_state.c:2058
 [<ffffffff832c1f7a>] xfrm_init_state+0x1a/0x20 net/xfrm/xfrm_state.c:2084