====================================================== [ INFO: possible circular locking dependency detected ] 4.9.205-syzkaller #0 Not tainted ------------------------------------------------------- syz-executor.4/11432 is trying to acquire lock: (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<00000000a6edba74>] inode_lock include/linux/fs.h:771 [inline] (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<00000000a6edba74>] shmem_fallocate+0x143/0xab0 mm/shmem.c:2683 but task is already holding lock: (ashmem_mutex){+.+.+.}, at: [<0000000046fcff92>] ashmem_shrink_scan+0x56/0x4c0 drivers/staging/android/ashmem.c:455 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: lock_acquire+0x133/0x3d0 kernel/locking/lockdep.c:3759 __mutex_lock_common kernel/locking/mutex.c:521 [inline] mutex_lock_nested+0xc7/0x920 kernel/locking/mutex.c:621 ashmem_mmap+0x53/0x470 drivers/staging/android/ashmem.c:378 mmap_region+0x7e7/0xfa0 mm/mmap.c:1726 do_mmap+0x539/0xbc0 mm/mmap.c:1505 do_mmap_pgoff include/linux/mm.h:2066 [inline] vm_mmap_pgoff+0x179/0x1c0 mm/util.c:329 SYSC_mmap_pgoff mm/mmap.c:1555 [inline] SyS_mmap_pgoff+0xfa/0x1b0 mm/mmap.c:1513 SYSC_mmap arch/x86/kernel/sys_x86_64.c:96 [inline] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:87 do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 entry_SYSCALL_64_after_swapgs+0x5d/0xdb lock_acquire+0x133/0x3d0 kernel/locking/lockdep.c:3759 down_read+0x44/0xb0 kernel/locking/rwsem.c:22 __do_page_fault+0x7bd/0xa60 arch/x86/mm/fault.c:1337 do_page_fault+0x28/0x30 arch/x86/mm/fault.c:1464 page_fault+0x25/0x30 arch/x86/entry/entry_64.S:956 generic_perform_write+0x1b6/0x500 mm/filemap.c:2930 __generic_file_write_iter+0x340/0x530 mm/filemap.c:3065 generic_file_write_iter+0x38a/0x630 mm/filemap.c:3093 new_sync_write fs/read_write.c:498 [inline] __vfs_write+0x3c1/0x560 fs/read_write.c:511 vfs_write+0x185/0x520 fs/read_write.c:559 SYSC_write fs/read_write.c:607 [inline] SyS_write+0x121/0x270 fs/read_write.c:599 do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 entry_SYSCALL_64_after_swapgs+0x5d/0xdb check_prev_add kernel/locking/lockdep.c:1828 [inline] check_prevs_add kernel/locking/lockdep.c:1938 [inline] validate_chain kernel/locking/lockdep.c:2265 [inline] __lock_acquire+0x2d22/0x4390 kernel/locking/lockdep.c:3345 lock_acquire+0x133/0x3d0 kernel/locking/lockdep.c:3759 down_write+0x41/0xa0 kernel/locking/rwsem.c:52 inode_lock include/linux/fs.h:771 [inline] shmem_fallocate+0x143/0xab0 mm/shmem.c:2683 ashmem_shrink_scan drivers/staging/android/ashmem.c:462 [inline] ashmem_shrink_scan+0x1c3/0x4c0 drivers/staging/android/ashmem.c:446 ashmem_ioctl+0x29b/0xdd0 drivers/staging/android/ashmem.c:804 vfs_ioctl fs/ioctl.c:43 [inline] file_ioctl fs/ioctl.c:493 [inline] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 SYSC_ioctl fs/ioctl.c:694 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 entry_SYSCALL_64_after_swapgs+0x5d/0xdb 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-executor.4/11432: #0: (ashmem_mutex){+.+.+.}, at: [<0000000046fcff92>] ashmem_shrink_scan+0x56/0x4c0 drivers/staging/android/ashmem.c:455 stack backtrace: CPU: 1 PID: 11432 Comm: syz-executor.4 Not tainted 4.9.205-syzkaller #0 ffff8801b6c276b8 ffffffff81b55e6b ffffffff83cb7ca0 ffffffff83cd9db0 ffffffff83cae4c0 ffffffff8424ff40 ffff8801b50d5f00 ffff8801b6c27710 ffffffff81406e9a ffffffff81bbc4cc ffffffff8406cac0 ffff8801b50d67d8 Call Trace: [<000000004beab808>] __dump_stack lib/dump_stack.c:15 [inline] [<000000004beab808>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<00000000f554de8d>] print_circular_bug.cold+0x2f6/0x454 kernel/locking/lockdep.c:1202 [<000000003e00c23f>] check_prev_add kernel/locking/lockdep.c:1828 [inline] [<000000003e00c23f>] check_prevs_add kernel/locking/lockdep.c:1938 [inline] [<000000003e00c23f>] validate_chain kernel/locking/lockdep.c:2265 [inline] [<000000003e00c23f>] __lock_acquire+0x2d22/0x4390 kernel/locking/lockdep.c:3345 [<00000000f97f0f3c>] lock_acquire+0x133/0x3d0 kernel/locking/lockdep.c:3759 [<00000000d7170e9c>] down_write+0x41/0xa0 kernel/locking/rwsem.c:52 [<00000000a6edba74>] inode_lock include/linux/fs.h:771 [inline] [<00000000a6edba74>] shmem_fallocate+0x143/0xab0 mm/shmem.c:2683 [<0000000094ce0dee>] ashmem_shrink_scan drivers/staging/android/ashmem.c:462 [inline] [<0000000094ce0dee>] ashmem_shrink_scan+0x1c3/0x4c0 drivers/staging/android/ashmem.c:446 [<000000009050bfbf>] ashmem_ioctl+0x29b/0xdd0 drivers/staging/android/ashmem.c:804 [<000000009797d90e>] vfs_ioctl fs/ioctl.c:43 [inline] [<000000009797d90e>] file_ioctl fs/ioctl.c:493 [inline] [<000000009797d90e>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<0000000038d72b02>] SYSC_ioctl fs/ioctl.c:694 [inline] [<0000000038d72b02>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000004ca6c4d4>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000365840c0>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb