======================================================
[ INFO: possible circular locking dependency detected ]
4.4.120-gd63fdf6 #29 Not tainted
-------------------------------------------------------
syz-executor4/8305 is trying to acquire lock:
 (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<ffffffff81463361>] shmem_file_llseek+0xf1/0x240 mm/shmem.c:1816
audit: type=1400 audit(1521405250.861:26): avc:  denied  { setopt } for  pid=8315 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

but task is already holding lock:
device bridge0 entered promiscuous mode
 (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
       [<ffffffff81006d91>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
       [<ffffffff81006d91>] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459
       [<ffffffff837752ea>] sysenter_flags_fixed+0xd/0x17

       [<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
       [<ffffffff8151e6db>] vfs_llseek fs/read_write.c:260 [inline]
       [<ffffffff8151e6db>] SYSC_lseek fs/read_write.c:285 [inline]
       [<ffffffff8151e6db>] SyS_lseek fs/read_write.c:276 [inline]
       [<ffffffff8151e6db>] C_SYSC_lseek fs/read_write.c:297 [inline]
       [<ffffffff8151e6db>] compat_SyS_lseek+0xeb/0x170 fs/read_write.c:295
       [<ffffffff81006d91>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
       [<ffffffff81006d91>] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459
       [<ffffffff837752ea>] sysenter_flags_fixed+0xd/0x17

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-executor4/8305:
 #0:  (ashmem_mutex){+.+.+.}, at: [<ffffffff82c62016>] ashmem_llseek+0x56/0x1f0 drivers/staging/android/ashmem.c:330

stack backtrace:
CPU: 1 PID: 8305 Comm: syz-executor4 Not tainted 4.4.120-gd63fdf6 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 98db34f3148c3d7e ffff8801cafc7a58 ffffffff81d0408d
 ffffffff851a0010 ffffffff851a9d00 ffffffff851be970 ffff8801c80a88f8
 ffff8801c80a8000 ffff8801cafc7aa0 ffffffff81233ba1 ffff8801c80a88f8
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
 [<ffffffff8151e6db>] vfs_llseek fs/read_write.c:260 [inline]
 [<ffffffff8151e6db>] SYSC_lseek fs/read_write.c:285 [inline]
 [<ffffffff8151e6db>] SyS_lseek fs/read_write.c:276 [inline]
 [<ffffffff8151e6db>] C_SYSC_lseek fs/read_write.c:297 [inline]
 [<ffffffff8151e6db>] compat_SyS_lseek+0xeb/0x170 fs/read_write.c:295
 [<ffffffff81006d91>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d91>] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459
 [<ffffffff837752ea>] sysenter_flags_fixed+0xd/0x17
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
binder: 8569:8571 ioctl c018620b 20000040 returned -14
binder: BINDER_SET_CONTEXT_MGR already set
binder: 8569:8571 ioctl 40046207 0 returned -16
device lo entered promiscuous mode
binder: 8569:8583 ioctl c018620b 20000040 returned -14
device lo left promiscuous mode
device lo entered promiscuous mode
device lo left promiscuous mode
proc: unrecognized mount option "©" or missing value
proc: unrecognized mount option "©" or missing value
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
audit: type=1400 audit(1521405253.201:27): avc:  denied  { create } for  pid=8665 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(1521405253.251:28): avc:  denied  { getopt } for  pid=8691 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_netfilter_socket permissive=1
audit: type=1400 audit(1521405253.271:29): avc:  denied  { write } for  pid=8665 comm="syz-executor1" path="socket:[19413]" dev="sockfs" ino=19413 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(1521405253.331:30): avc:  denied  { setopt } for  pid=8717 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=netlink_generic_socket permissive=1
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=39479 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=39479 sclass=netlink_route_socket
binder: 9132:9135 transaction failed 29189/-22, size 32-0 line 3005
binder: BINDER_SET_CONTEXT_MGR already set
binder: 9132:9138 ioctl 40046207 0 returned -16
binder_alloc: 9132: binder_alloc_buf, no vma
binder: 9132:9138 transaction failed 29189/-3, size 32-0 line 3128
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29189
binder: 9144:9145 ioctl c0306201 20008000 returned -14
binder: BINDER_SET_CONTEXT_MGR already set
binder: 9144:9145 ioctl 40046207 0 returned -16
binder: 9144:9146 ioctl c0306201 20008000 returned -14
IPv4: Oversized IP packet from 127.0.0.1
IPv4: Oversized IP packet from 127.0.0.1
TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
binder: 9265:9271 ioctl 40046205 101 returned -22
binder: 9265:9271 ioctl 400454d1 20000140 returned -22
binder: 9265:9271 ioctl 40046205 101 returned -22
binder: 9265:9282 ioctl 400454d1 20000140 returned -22
TCP: request_sock_TCP: Possible SYN flooding on port 20000. Sending cookies.  Check SNMP counters.
binder: 9348:9356 ioctl c018620b 20000040 returned -14
binder: 9348:9360 ioctl c018620b 20000040 returned -14
audit: type=1326 audit(1521405257.101:31): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=9394 comm="syz-executor3" exe="/root/syz-executor3" sig=31 arch=40000003 syscall=240 compat=1 ip=0xf7768ba9 code=0x0
audit: type=1326 audit(1521405257.141:32): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=9394 comm="syz-executor3" exe="/root/syz-executor3" sig=31 arch=40000003 syscall=240 compat=1 ip=0xf7768ba9 code=0x0
sg_write: data in/out 2020961861/197 bytes for SCSI command 0x0-- guessing data in;
   program syz-executor5 not setting count and/or reply_len properly
SELinux:  policydb magic number 0x0 does not match expected magic number 0xf97cff8c
l2tp_ppp: tunl 4: set debug=9d59c0f
syz-executor6 (9646): /proc/9645/oom_adj is deprecated, please use /proc/9645/oom_score_adj instead.
audit: type=1400 audit(1521405258.981:33): avc:  denied  { getopt } for  pid=9774 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_generic_socket permissive=1
binder: 10099:10106 ioctl c0306201 20000300 returned -14
binder_alloc: binder_alloc_mmap_handler: 10099 20000000-20001000 already mapped failed -16
binder: 10099:10111 ioctl c0306201 20000300 returned -14