Hello, syzbot found the following issue on: HEAD commit: 8ecfa36c Merge tag 'riscv-for-linus-5.13-rc6' of git://git.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17121304300000 kernel config: https://syzkaller.appspot.com/x/.config?x=547a5e42ca601229 dashboard link: https://syzkaller.appspot.com/bug?extid=6a8a0d93c91e8fbf2e80 compiler: Debian clang version 11.0.1-2 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17065d1fd00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12de53afd00000 The issue was bisected to: commit 5befc7c26e5a98cd49789fb1beb52c62bd472dba Author: Keith Busch <kbusch@xxxxxxxxxx> Date: Wed Mar 24 23:18:05 2021 +0000 nvme: implement non-mdts command limits bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15e62857d00000 final oops: https://syzkaller.appspot.com/x/report.txt?x=17e62857d00000 console output: https://syzkaller.appspot.com/x/log.txt?x=13e62857d00000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+6a8a0d93c91e8fbf2e80@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: 5befc7c26e5a ("nvme: implement non-mdts command limits") ====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc5-syzkaller #0 Not tainted ------------------------------------------------------ systemd-udevd/8445 is trying to acquire lock: ffffffff8d671688 (loop_ctl_mutex){+.+.}-{3:3}, at: loop_probe+0xe1/0x220 drivers/block/loop.c:2234 but task is already holding lock: ffffffff8d4db008 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x2f/0x1c0 block/genhd.c:680 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (major_names_lock){+.+.}-{3:3}: lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 __register_blkdev+0x2c/0x360 block/genhd.c:223 register_mtd_blktrans+0x94/0x3d0 drivers/mtd/mtd_blkdevs.c:534 do_one_initcall+0x1a7/0x400 init/main.c:1249 do_initcall_level+0x14a/0x1f5 init/main.c:1322 do_initcalls+0x4b/0x8c init/main.c:1338 kernel_init_freeable+0x3fd/0x58a init/main.c:1560 kernel_init+0xd/0x290 init/main.c:1447 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 -> #2 (mtd_table_mutex){+.+.}-{3:3}: lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 blktrans_open+0x61/0x430 drivers/mtd/mtd_blkdevs.c:212 __blkdev_get+0x293/0xa50 fs/block_dev.c:1311 blkdev_get_by_dev+0xf9/0x640 fs/block_dev.c:1451 blkdev_open+0x132/0x2c0 fs/block_dev.c:1546 do_dentry_open+0x7cb/0x1010 fs/open.c:826 do_open fs/namei.c:3361 [inline] path_openat+0x28e6/0x39b0 fs/namei.c:3494 do_filp_open+0x221/0x460 fs/namei.c:3521 do_sys_openat2+0x124/0x460 fs/open.c:1187 do_sys_open fs/open.c:1203 [inline] __do_sys_open fs/open.c:1211 [inline] __se_sys_open fs/open.c:1207 [inline] __x64_sys_open+0x221/0x270 fs/open.c:1207 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #1 (&bdev->bd_mutex){+.+.}-{3:3}: lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 del_gendisk+0x2ab/0x860 block/genhd.c:610 loop_remove drivers/block/loop.c:2180 [inline] loop_control_ioctl+0x62c/0x770 drivers/block/loop.c:2280 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:1069 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #0 (loop_ctl_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2938 [inline] check_prevs_add+0x4f9/0x5b60 kernel/locking/lockdep.c:3061 validate_chain kernel/locking/lockdep.c:3676 [inline] __lock_acquire+0x4307/0x6040 kernel/locking/lockdep.c:4902 lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 loop_probe+0xe1/0x220 drivers/block/loop.c:2234 blk_request_module+0x19d/0x1c0 block/genhd.c:683 blkdev_get_no_open+0x44/0x1f0 fs/block_dev.c:1374 blkdev_get_by_dev+0x82/0x640 fs/block_dev.c:1437 blkdev_open+0x132/0x2c0 fs/block_dev.c:1546 do_dentry_open+0x7cb/0x1010 fs/open.c:826 do_open fs/namei.c:3361 [inline] path_openat+0x28e6/0x39b0 fs/namei.c:3494 do_filp_open+0x221/0x460 fs/namei.c:3521 do_sys_openat2+0x124/0x460 fs/open.c:1187 do_sys_open fs/open.c:1203 [inline] __do_sys_open fs/open.c:1211 [inline] __se_sys_open fs/open.c:1207 [inline] __x64_sys_open+0x221/0x270 fs/open.c:1207 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: loop_ctl_mutex --> mtd_table_mutex --> major_names_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(major_names_lock); lock(mtd_table_mutex); lock(major_names_lock); lock(loop_ctl_mutex); *** DEADLOCK *** 1 lock held by systemd-udevd/8445: #0: ffffffff8d4db008 (major_names_lock){+.+.}-{3:3}, at: blk_request_module+0x2f/0x1c0 block/genhd.c:680 stack backtrace: CPU: 1 PID: 8445 Comm: systemd-udevd Not tainted 5.13.0-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:79 [inline] dump_stack+0x202/0x31e lib/dump_stack.c:120 print_circular_bug+0xb17/0xdc0 kernel/locking/lockdep.c:2007 check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2129 check_prev_add kernel/locking/lockdep.c:2938 [inline] check_prevs_add+0x4f9/0x5b60 kernel/locking/lockdep.c:3061 validate_chain kernel/locking/lockdep.c:3676 [inline] __lock_acquire+0x4307/0x6040 kernel/locking/lockdep.c:4902 lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5512 __mutex_lock_common+0x1bf/0x3100 kernel/locking/mutex.c:959 __mutex_lock kernel/locking/mutex.c:1104 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1119 loop_probe+0xe1/0x220 drivers/block/loop.c:2234 blk_request_module+0x19d/0x1c0 block/genhd.c:683 blkdev_get_no_open+0x44/0x1f0 fs/block_dev.c:1374 blkdev_get_by_dev+0x82/0x640 fs/block_dev.c:1437 blkdev_open+0x132/0x2c0 fs/block_dev.c:1546 do_dentry_open+0x7cb/0x1010 fs/open.c:826 do_open fs/namei.c:3361 [inline] path_openat+0x28e6/0x39b0 fs/namei.c:3494 do_filp_open+0x221/0x460 fs/namei.c:3521 do_sys_openat2+0x124/0x460 fs/open.c:1187 do_sys_open fs/open.c:1203 [inline] __do_sys_open fs/open.c:1211 [inline] __se_sys_open fs/open.c:1207 [inline] __x64_sys_open+0x221/0x270 fs/open.c:1207 do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f666c06a840 Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24 RSP: 002b:00007ffc880be598 EFLAGS: 00000246 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 000055dd2c8278f0 RCX: 00007f666c06a840 RDX: 000055dd2c52efe3 RSI: 00000000000a0800 RDI: 000055dd2c827830 RBP: 00007ffc880be710 R08: 000055dd2c52e670 R09: 0000000000000010 R10: 000055dd2c52ed0c R11: 0000000000000246 R12: 00007ffc880be660 R13: 000055dd2c829010 R14: 0000000000000003 R15: 000000000000000e --- 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. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this issue, for details see: https://goo.gl/tpsmEJ#testing-patches
