syzbot has found a reproducer for the following crash on: HEAD commit: 11ba4688 Linux 5.8-rc5 git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=175391fb100000 kernel config: https://syzkaller.appspot.com/x/.config?x=a160d1053fc89af5 dashboard link: https://syzkaller.appspot.com/bug?extid=7a0d9d0b26efefe61780 compiler: gcc (GCC) 10.1.0-syz 20200507 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=104d9c77100000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1343e95d100000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+7a0d9d0b26efefe61780@xxxxxxxxxxxxxxxxxxxxxxxxx ====================================================== WARNING: possible circular locking dependency detected 5.8.0-rc5-syzkaller #0 Not tainted ------------------------------------------------------ khugepaged/1158 is trying to acquire lock: ffff8882071865b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:800 [inline] ffff8882071865b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: shmem_fallocate+0x153/0xd90 mm/shmem.c:2707 but task is already holding lock: ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: fs_reclaim_release mm/page_alloc.c:4202 [inline] ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: fs_reclaim_release mm/page_alloc.c:4198 [inline] ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:4227 [inline] ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:4244 [inline] ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath.constprop.0+0x1554/0x2780 mm/page_alloc.c:4650 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4183 [inline] fs_reclaim_acquire mm/page_alloc.c:4194 [inline] prepare_alloc_pages mm/page_alloc.c:4780 [inline] __alloc_pages_nodemask+0x3d1/0x930 mm/page_alloc.c:4832 alloc_pages_vma+0xdd/0x720 mm/mempolicy.c:2255 shmem_alloc_page+0x11f/0x1f0 mm/shmem.c:1502 shmem_alloc_and_acct_page+0x161/0x8a0 mm/shmem.c:1527 shmem_getpage_gfp+0x511/0x2450 mm/shmem.c:1823 shmem_getpage mm/shmem.c:153 [inline] shmem_write_begin+0xf9/0x1d0 mm/shmem.c:2459 generic_perform_write+0x20a/0x4f0 mm/filemap.c:3318 __generic_file_write_iter+0x24b/0x610 mm/filemap.c:3447 generic_file_write_iter+0x3a6/0x5c0 mm/filemap.c:3479 call_write_iter include/linux/fs.h:1908 [inline] new_sync_write+0x422/0x650 fs/read_write.c:503 vfs_write+0x59d/0x6b0 fs/read_write.c:578 ksys_write+0x12d/0x250 fs/read_write.c:631 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain kernel/locking/lockdep.c:3218 [inline] __lock_acquire+0x2acb/0x56e0 kernel/locking/lockdep.c:4380 lock_acquire+0x1f1/0xad0 kernel/locking/lockdep.c:4959 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 inode_lock include/linux/fs.h:800 [inline] shmem_fallocate+0x153/0xd90 mm/shmem.c:2707 ashmem_shrink_scan.part.0+0x2e9/0x490 drivers/staging/android/ashmem.c:490 ashmem_shrink_scan+0x6c/0xa0 drivers/staging/android/ashmem.c:473 do_shrink_slab+0x3c6/0xab0 mm/vmscan.c:518 shrink_slab+0x16f/0x5c0 mm/vmscan.c:679 shrink_node_memcgs mm/vmscan.c:2658 [inline] shrink_node+0x519/0x1b60 mm/vmscan.c:2770 shrink_zones mm/vmscan.c:2973 [inline] do_try_to_free_pages+0x38b/0x1340 mm/vmscan.c:3026 try_to_free_pages+0x29a/0x8b0 mm/vmscan.c:3265 __perform_reclaim mm/page_alloc.c:4223 [inline] __alloc_pages_direct_reclaim mm/page_alloc.c:4244 [inline] __alloc_pages_slowpath.constprop.0+0x949/0x2780 mm/page_alloc.c:4650 __alloc_pages_nodemask+0x68f/0x930 mm/page_alloc.c:4863 __alloc_pages include/linux/gfp.h:509 [inline] __alloc_pages_node include/linux/gfp.h:522 [inline] khugepaged_alloc_page+0xa0/0x170 mm/khugepaged.c:867 collapse_huge_page mm/khugepaged.c:1056 [inline] khugepaged_scan_pmd mm/khugepaged.c:1349 [inline] khugepaged_scan_mm_slot mm/khugepaged.c:2110 [inline] khugepaged_do_scan mm/khugepaged.c:2193 [inline] khugepaged+0x3093/0x5a10 mm/khugepaged.c:2238 kthread+0x3b5/0x4a0 kernel/kthread.c:291 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#15); lock(fs_reclaim); lock(&sb->s_type->i_mutex_key#15); *** DEADLOCK *** 2 locks held by khugepaged/1158: #0: ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: fs_reclaim_release mm/page_alloc.c:4202 [inline] #0: ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: fs_reclaim_release mm/page_alloc.c:4198 [inline] #0: ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: __perform_reclaim mm/page_alloc.c:4227 [inline] #0: ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_direct_reclaim mm/page_alloc.c:4244 [inline] #0: ffffffff89c6c260 (fs_reclaim){+.+.}-{0:0}, at: __alloc_pages_slowpath.constprop.0+0x1554/0x2780 mm/page_alloc.c:4650 #1: ffffffff89c46a90 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0xc7/0x5c0 mm/vmscan.c:669 stack backtrace: CPU: 1 PID: 1158 Comm: khugepaged Not tainted 5.8.0-rc5-syzkaller #0 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+0x18f/0x20d lib/dump_stack.c:118 check_noncircular+0x324/0x3e0 kernel/locking/lockdep.c:1827 check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain kernel/locking/lockdep.c:3218 [inline] __lock_acquire+0x2acb/0x56e0 kernel/locking/lockdep.c:4380 lock_acquire+0x1f1/0xad0 kernel/locking/lockdep.c:4959 down_write+0x8d/0x150 kernel/locking/rwsem.c:1531 inode_lock include/linux/fs.h:800 [inline] shmem_fallocate+0x153/0xd90 mm/shmem.c:2707 ashmem_shrink_scan.part.0+0x2e9/0x490 drivers/staging/android/ashmem.c:490 ashmem_shrink_scan+0x6c/0xa0 drivers/staging/android/ashmem.c:473 do_shrink_slab+0x3c6/0xab0 mm/vmscan.c:518 shrink_slab+0x16f/0x5c0 mm/vmscan.c:679 shrink_node_memcgs mm/vmscan.c:2658 [inline] shrink_node+0x519/0x1b60 mm/vmscan.c:2770 shrink_zones mm/vmscan.c:2973 [inline] do_try_to_free_pages+0x38b/0x1340 mm/vmscan.c:3026 try_to_free_pages+0x29a/0x8b0 mm/vmscan.c:3265 __perform_reclaim mm/page_alloc.c:4223 [inline] __alloc_pages_direct_reclaim mm/page_alloc.c:4244 [inline] __alloc_pages_slowpath.constprop.0+0x949/0x2780 mm/page_alloc.c:4650 __alloc_pages_nodemask+0x68f/0x930 mm/page_alloc.c:4863 __alloc_pages include/linux/gfp.h:509 [inline] __alloc_pages_node include/linux/gfp.h:522 [inline] khugepaged_alloc_page+0xa0/0x170 mm/khugepaged.c:867 collapse_huge_page mm/khugepaged.c:1056 [inline] khugepaged_scan_pmd mm/khugepaged.c:1349 [inline] khugepaged_scan_mm_slot mm/khugepaged.c:2110 [inline] khugepaged_do_scan mm/khugepaged.c:2193 [inline] khugepaged+0x3093/0x5a10 mm/khugepaged.c:2238 kthread+0x3b5/0x4a0 kernel/kthread.c:291 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
