Hello, syzbot found the following issue on: HEAD commit: 950b879b7f02 riscv: Fixup race condition on PG_dcache_clea.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes console output: https://syzkaller.appspot.com/x/log.txt?x=171f6afa280000 kernel config: https://syzkaller.appspot.com/x/.config?x=ecebece1b90c0342 dashboard link: https://syzkaller.appspot.com/bug?extid=6c9dbef55920042a75f7 compiler: riscv64-linux-gnu-gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 userspace arch: riscv64 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/5ab53d394dbf/non_bootable_disk-950b879b.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/938475579d6c/vmlinux-950b879b.xz kernel image: https://storage.googleapis.com/syzbot-assets/bcf263d8c574/Image-950b879b.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+6c9dbef55920042a75f7@xxxxxxxxxxxxxxxxxxxxxxxxx 523776 pages RAM 0 pages HighMem/MovableOnly 184025 pages reserved 4096 pages cma reserved ====================================================== WARNING: possible circular locking dependency detected 6.2.0-rc1-syzkaller #0 Tainted: G W ------------------------------------------------------ syz-executor.0/4635 is trying to acquire lock: ffffffff8505b470 (cpu_hotplug_lock){++++}-{0:0}, at: cpus_read_lock+0x14/0x1c kernel/cpu.c:310 but task is already holding lock: ffffffff851ad348 (freezer_mutex){+.+.}-{3:3}, at: freezer_change_state kernel/cgroup/legacy_freezer.c:387 [inline] ffffffff851ad348 (freezer_mutex){+.+.}-{3:3}, at: freezer_write+0xa0/0x866 kernel/cgroup/legacy_freezer.c:426 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (freezer_mutex){+.+.}-{3:3}: lock_acquire.part.0+0x1d0/0x424 kernel/locking/lockdep.c:5668 lock_acquire+0x54/0x6a kernel/locking/lockdep.c:5641 __mutex_lock_common kernel/locking/mutex.c:603 [inline] __mutex_lock+0x114/0xb42 kernel/locking/mutex.c:747 mutex_lock_nested+0x14/0x1c kernel/locking/mutex.c:799 freezer_attach+0x96/0x19a kernel/cgroup/legacy_freezer.c:163 cgroup_migrate_execute+0x818/0xa3a kernel/cgroup/cgroup.c:2621 cgroup_migrate kernel/cgroup/cgroup.c:2877 [inline] cgroup_attach_task+0x418/0x7ac kernel/cgroup/cgroup.c:2910 __cgroup1_procs_write.constprop.0+0x250/0x2be kernel/cgroup/cgroup-v1.c:523 cgroup1_procs_write+0x24/0x32 kernel/cgroup/cgroup-v1.c:536 cgroup_file_write+0x1b2/0x3b8 kernel/cgroup/cgroup.c:4061 kernfs_fop_write_iter+0x264/0x32e fs/kernfs/file.c:334 call_write_iter include/linux/fs.h:2186 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x4a4/0x568 fs/read_write.c:584 ksys_write+0x10a/0x224 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] sys_write+0x28/0x36 fs/read_write.c:646 ret_from_syscall+0x0/0x2 -> #1 (cgroup_threadgroup_rwsem){++++}-{0:0}: lock_acquire.part.0+0x1d0/0x424 kernel/locking/lockdep.c:5668 lock_acquire+0x54/0x6a kernel/locking/lockdep.c:5641 percpu_down_write+0x4e/0x1d4 kernel/locking/percpu-rwsem.c:227 cgroup_attach_lock kernel/cgroup/cgroup.c:2437 [inline] cgroup_procs_write_start+0x12a/0x46c kernel/cgroup/cgroup.c:2939 __cgroup_procs_write+0xc2/0x3be kernel/cgroup/cgroup.c:5139 cgroup_procs_write+0x22/0x48 kernel/cgroup/cgroup.c:5175 cgroup_file_write+0x1b2/0x3b8 kernel/cgroup/cgroup.c:4061 kernfs_fop_write_iter+0x264/0x32e fs/kernfs/file.c:334 call_write_iter include/linux/fs.h:2186 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x4a4/0x568 fs/read_write.c:584 ksys_write+0x10a/0x224 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] sys_write+0x28/0x36 fs/read_write.c:646 ret_from_syscall+0x0/0x2 -> #0 (cpu_hotplug_lock){++++}-{0:0}: check_noncircular+0x1de/0x1fe kernel/locking/lockdep.c:2177 check_prev_add kernel/locking/lockdep.c:3097 [inline] check_prevs_add kernel/locking/lockdep.c:3216 [inline] validate_chain kernel/locking/lockdep.c:3831 [inline] __lock_acquire+0x198a/0x347a kernel/locking/lockdep.c:5055 lock_acquire.part.0+0x1d0/0x424 kernel/locking/lockdep.c:5668 lock_acquire+0x54/0x6a kernel/locking/lockdep.c:5641 percpu_down_read.constprop.0+0x40/0x216 include/linux/percpu-rwsem.h:51 cpus_read_lock+0x14/0x1c kernel/cpu.c:310 static_key_slow_inc+0x1e/0x6a kernel/jump_label.c:185 freezer_apply_state+0x156/0x17c kernel/cgroup/legacy_freezer.c:353 freezer_change_state kernel/cgroup/legacy_freezer.c:398 [inline] freezer_write+0x552/0x866 kernel/cgroup/legacy_freezer.c:426 cgroup_file_write+0x1b2/0x3b8 kernel/cgroup/cgroup.c:4061 kernfs_fop_write_iter+0x264/0x32e fs/kernfs/file.c:334 call_write_iter include/linux/fs.h:2186 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x4a4/0x568 fs/read_write.c:584 ksys_write+0x10a/0x224 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] sys_write+0x28/0x36 fs/read_write.c:646 ret_from_syscall+0x0/0x2 other info that might help us debug this: Chain exists of: cpu_hotplug_lock --> cgroup_threadgroup_rwsem --> freezer_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(freezer_mutex); lock(cgroup_threadgroup_rwsem); lock(freezer_mutex); lock(cpu_hotplug_lock); *** DEADLOCK *** 5 locks held by syz-executor.0/4635: #0: ff6000001455f4e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xc2/0xc4 fs/file.c:1046 #1: ff6000000fa6a460 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x1e8/0x568 fs/read_write.c:580 #2: ff60000027486c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1fc/0x32e fs/kernfs/file.c:325 #3: ff60000014ce31d8 (kn->active#13){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20e/0x32e fs/kernfs/file.c:326 #4: ffffffff851ad348 (freezer_mutex){+.+.}-{3:3}, at: freezer_change_state kernel/cgroup/legacy_freezer.c:387 [inline] #4: ffffffff851ad348 (freezer_mutex){+.+.}-{3:3}, at: freezer_write+0xa0/0x866 kernel/cgroup/legacy_freezer.c:426 stack backtrace: CPU: 0 PID: 4635 Comm: syz-executor.0 Tainted: G W 6.2.0-rc1-syzkaller #0 Hardware name: riscv-virtio,qemu (DT) Call Trace: [<ffffffff8000b9ea>] dump_backtrace+0x2e/0x3c arch/riscv/kernel/stacktrace.c:121 [<ffffffff83402b96>] show_stack+0x34/0x40 arch/riscv/kernel/stacktrace.c:127 [<ffffffff83442726>] __dump_stack lib/dump_stack.c:88 [inline] [<ffffffff83442726>] dump_stack_lvl+0xe0/0x14c lib/dump_stack.c:106 [<ffffffff834427ae>] dump_stack+0x1c/0x24 lib/dump_stack.c:113 [<ffffffff8012199a>] print_circular_bug+0x370/0x3fa kernel/locking/lockdep.c:2055 [<ffffffff80121c02>] check_noncircular+0x1de/0x1fe kernel/locking/lockdep.c:2177 [<ffffffff80125e68>] check_prev_add kernel/locking/lockdep.c:3097 [inline] [<ffffffff80125e68>] check_prevs_add kernel/locking/lockdep.c:3216 [inline] [<ffffffff80125e68>] validate_chain kernel/locking/lockdep.c:3831 [inline] [<ffffffff80125e68>] __lock_acquire+0x198a/0x347a kernel/locking/lockdep.c:5055 [<ffffffff80128932>] lock_acquire.part.0+0x1d0/0x424 kernel/locking/lockdep.c:5668 [<ffffffff80128bda>] lock_acquire+0x54/0x6a kernel/locking/lockdep.c:5641 [<ffffffff8005b3f6>] percpu_down_read.constprop.0+0x40/0x216 include/linux/percpu-rwsem.h:51 [<ffffffff8005b5e0>] cpus_read_lock+0x14/0x1c kernel/cpu.c:310 [<ffffffff8037974e>] static_key_slow_inc+0x1e/0x6a kernel/jump_label.c:185 [<ffffffff801f863c>] freezer_apply_state+0x156/0x17c kernel/cgroup/legacy_freezer.c:353 [<ffffffff801f912c>] freezer_change_state kernel/cgroup/legacy_freezer.c:398 [inline] [<ffffffff801f912c>] freezer_write+0x552/0x866 kernel/cgroup/legacy_freezer.c:426 [<ffffffff801d9e1e>] cgroup_file_write+0x1b2/0x3b8 kernel/cgroup/cgroup.c:4061 [<ffffffff806c57c4>] kernfs_fop_write_iter+0x264/0x32e fs/kernfs/file.c:334 [<ffffffff80548b2c>] call_write_iter include/linux/fs.h:2186 [inline] [<ffffffff80548b2c>] new_sync_write fs/read_write.c:491 [inline] [<ffffffff80548b2c>] vfs_write+0x4a4/0x568 fs/read_write.c:584 [<ffffffff80548f54>] ksys_write+0x10a/0x224 fs/read_write.c:637 [<ffffffff80549096>] __do_sys_write fs/read_write.c:649 [inline] [<ffffffff80549096>] sys_write+0x28/0x36 fs/read_write.c:646 [<ffffffff80005ff6>] ret_from_syscall+0x0/0x2 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the bug is already fixed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to change bug's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the bug is a duplicate of another bug, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
