====================================================== WARNING: possible circular locking dependency detected 5.0.0-rc4+ #55 Not tainted ------------------------------------------------------ syz-executor056/8093 is trying to acquire lock: 000000009f0c249a (&mm->mmap_sem){++++}, at: do_user_addr_fault arch/x86/mm/fault.c:1426 [inline] 000000009f0c249a (&mm->mmap_sem){++++}, at: __do_page_fault+0x9c2/0xd60 arch/x86/mm/fault.c:1541 but task is already holding lock: 00000000c04ead3e (&sb->s_type->i_mutex_key#12){+.+.}, at: inode_lock include/linux/fs.h:757 [inline] 00000000c04ead3e (&sb->s_type->i_mutex_key#12){+.+.}, at: generic_file_write_iter+0xe5/0x6a0 mm/filemap.c:3358 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&sb->s_type->i_mutex_key#12){+.+.}: down_write+0x8a/0x130 kernel/locking/rwsem.c:70 inode_lock include/linux/fs.h:757 [inline] shmem_fallocate+0x168/0x1200 mm/shmem.c:2633 ashmem_shrink_scan drivers/staging/android/ashmem.c:455 [inline] ashmem_shrink_scan+0x239/0x630 drivers/staging/android/ashmem.c:439 ashmem_ioctl+0x38a/0x12c0 drivers/staging/android/ashmem.c:797 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (ashmem_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 ashmem_mmap+0x55/0x520 drivers/staging/android/ashmem.c:361 call_mmap include/linux/fs.h:1868 [inline] mmap_region+0xde5/0x1ca0 mm/mmap.c:1786 do_mmap+0xa09/0x1220 mm/mmap.c:1559 do_mmap_pgoff include/linux/mm.h:2379 [inline] vm_mmap_pgoff+0x20b/0x2b0 mm/util.c:350 ksys_mmap_pgoff+0x4f8/0x650 mm/mmap.c:1609 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline] __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&mm->mmap_sem){++++}: lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 down_read+0x8d/0x120 kernel/locking/rwsem.c:24 do_user_addr_fault arch/x86/mm/fault.c:1426 [inline] __do_page_fault+0x9c2/0xd60 arch/x86/mm/fault.c:1541 do_page_fault+0xe6/0x7d8 arch/x86/mm/fault.c:1572 page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143 fault_in_pages_readable include/linux/pagemap.h:611 [inline] iov_iter_fault_in_readable+0x377/0x450 lib/iov_iter.c:425 generic_perform_write+0x202/0x6b0 mm/filemap.c:3198 __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333 generic_file_write_iter+0x34e/0x6a0 mm/filemap.c:3361 call_write_iter include/linux/fs.h:1863 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x764/0xb40 fs/read_write.c:487 vfs_write+0x20c/0x580 fs/read_write.c:549 ksys_write+0x105/0x260 fs/read_write.c:598 __do_sys_write fs/read_write.c:610 [inline] __se_sys_write fs/read_write.c:607 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:607 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#12 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sb->s_type->i_mutex_key#12); lock(ashmem_mutex); lock(&sb->s_type->i_mutex_key#12); lock(&mm->mmap_sem); *** DEADLOCK *** 2 locks held by syz-executor056/8093: #0: 00000000ef40b124 (sb_writers#5){.+.+}, at: file_start_write include/linux/fs.h:2816 [inline] #0: 00000000ef40b124 (sb_writers#5){.+.+}, at: vfs_write+0x429/0x580 fs/read_write.c:548 #1: 00000000c04ead3e (&sb->s_type->i_mutex_key#12){+.+.}, at: inode_lock include/linux/fs.h:757 [inline] #1: 00000000c04ead3e (&sb->s_type->i_mutex_key#12){+.+.}, at: generic_file_write_iter+0xe5/0x6a0 mm/filemap.c:3358 stack backtrace: CPU: 1 PID: 8093 Comm: syz-executor056 Not tainted 5.0.0-rc4+ #55 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1db/0x2d0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224 check_prev_add kernel/locking/lockdep.c:1866 [inline] check_prevs_add kernel/locking/lockdep.c:1979 [inline] validate_chain kernel/locking/lockdep.c:2350 [inline] __lock_acquire+0x3014/0x4a30 kernel/locking/lockdep.c:3338 lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 down_read+0x8d/0x120 kernel/locking/rwsem.c:24 do_user_addr_fault arch/x86/mm/fault.c:1426 [inline] __do_page_fault+0x9c2/0xd60 arch/x86/mm/fault.c:1541 do_page_fault+0xe6/0x7d8 arch/x86/mm/fault.c:1572 page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143 RIP: 0010:fault_in_pages_readable include/linux/pagemap.h:611 [inline] RIP: 0010:iov_iter_fault_in_readable+0x377/0x450 lib/iov_iter.c:425 Code: 89 f6 41 88 57 e0 e8 e8 ad f3 fd 45 85 f6 74 c1 e9 70 fe ff ff e8 59 ac f3 fd 0f 1f 00 0f ae e8 44 89 f0 48 8b 8d 68 ff ff ff <8a> 11 89 c3 0f 1f 00 41 88 57 d0 31 ff 89 de e8 b5 ad f3 fd 85 db RSP: 0018:ffff88808aaaf8a8 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000020e30c3f RDX: 0000000000000000 RSI: ffffffff838e5807 RDI: 0000000000000007 RBP: ffff88808aaaf948 R08: ffff88808fa4e600 R09: fffff94000423baf R10: fffff94000423bae R11: ffffea000211dd77 R12: 0000000000001000 R13: 0000000000001000 R14: 0000000000000000 R15: ffff88808aaaf920 generic_perform_write+0x202/0x6b0 mm/filemap.c:3198 __generic_file_write_iter+0x25e/0x630 mm/filemap.c:3333 generic_file_write_iter+0x34e/0x6a0 mm/filemap.c:3361 call_write_iter include/linux/fs.h:1863 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x764/0xb40 fs/read_write.c:487 vfs_write+0x20c/0x580 fs/read_write.c:549 ksys_write+0x105/0x260 fs/read_write.c:598 __do_sys_write fs/read_write.c:610 [inline] __se_sys_write fs/read_write.c:607 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:607 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4463d9 Code: e8 2c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fcb2406eda8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 00000000004463d9 RDX: 00000000fffffe43 RSI: 0000000020000c40 RDI: 0000000000000004 RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c R13: 0000000000000000 R14: 0080000080000000 R15: 20c49ba5e353f7cf