====================================================== WARNING: possible circular locking dependency detected 5.10.0-rc3-next-20201113-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.1/23213 is trying to acquire lock: ffffffff8bd20728 (brd_devices_mutex){+.+.}-{3:3}, at: brd_probe+0x31/0x250 drivers/block/brd.c:434 but task is already holding lock: ffffffff8bac2ac8 (major_names_lock){+.+.}-{3:3}, at: request_gendisk_module block/genhd.c:970 [inline] ffffffff8bac2ac8 (major_names_lock){+.+.}-{3:3}, at: get_gendisk+0x3c8/0x6a0 block/genhd.c:1023 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (major_names_lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x134/0x1110 kernel/locking/mutex.c:1103 __register_blkdev+0x2b/0x390 block/genhd.c:443 register_mtd_blktrans+0x85/0x3c0 drivers/mtd/mtd_blkdevs.c:534 do_one_initcall+0x103/0x650 init/main.c:1212 do_initcall_level init/main.c:1285 [inline] do_initcalls init/main.c:1301 [inline] do_basic_setup init/main.c:1321 [inline] kernel_init_freeable+0x600/0x684 init/main.c:1521 kernel_init+0xd/0x1b8 init/main.c:1410 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 -> #2 (mtd_table_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x134/0x1110 kernel/locking/mutex.c:1103 blktrans_open+0x69/0x600 drivers/mtd/mtd_blkdevs.c:212 __blkdev_get+0x80f/0x1870 fs/block_dev.c:1494 blkdev_get+0xd1/0x240 fs/block_dev.c:1634 blkdev_open+0x21d/0x2b0 fs/block_dev.c:1751 do_dentry_open+0x4b9/0x11b0 fs/open.c:817 do_open fs/namei.c:3252 [inline] path_openat+0x1b9a/0x2730 fs/namei.c:3369 do_filp_open+0x17e/0x3c0 fs/namei.c:3396 do_sys_openat2+0x16d/0x420 fs/open.c:1168 do_sys_open fs/open.c:1184 [inline] __do_sys_open fs/open.c:1192 [inline] __se_sys_open fs/open.c:1188 [inline] __x64_sys_open+0x119/0x1c0 fs/open.c:1188 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&bdev->bd_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x134/0x1110 kernel/locking/mutex.c:1103 __blkdev_get+0x457/0x1870 fs/block_dev.c:1479 blkdev_get+0xd1/0x240 fs/block_dev.c:1634 blkdev_get_by_dev+0x3b/0x70 fs/block_dev.c:1715 disk_scan_partitions block/genhd.c:671 [inline] register_disk block/genhd.c:721 [inline] __device_add_disk+0xe02/0x1250 block/genhd.c:808 add_disk include/linux/genhd.h:295 [inline] brd_init+0x2af/0x475 drivers/block/brd.c:518 do_one_initcall+0x103/0x650 init/main.c:1212 do_initcall_level init/main.c:1285 [inline] do_initcalls init/main.c:1301 [inline] do_basic_setup init/main.c:1321 [inline] kernel_init_freeable+0x600/0x684 init/main.c:1521 kernel_init+0xd/0x1b8 init/main.c:1410 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 -> #0 (brd_devices_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2866 [inline] check_prevs_add kernel/locking/lockdep.c:2991 [inline] validate_chain kernel/locking/lockdep.c:3606 [inline] __lock_acquire+0x2ca6/0x5c00 kernel/locking/lockdep.c:4830 lock_acquire kernel/locking/lockdep.c:5435 [inline] lock_acquire+0x2a3/0x8c0 kernel/locking/lockdep.c:5400 __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x134/0x1110 kernel/locking/mutex.c:1103 brd_probe+0x31/0x250 drivers/block/brd.c:434 request_gendisk_module block/genhd.c:973 [inline] get_gendisk+0x4c3/0x6a0 block/genhd.c:1023 bdev_get_gendisk fs/block_dev.c:1094 [inline] __blkdev_get+0x344/0x1870 fs/block_dev.c:1455 blkdev_get+0xd1/0x240 fs/block_dev.c:1634 blkdev_open+0x21d/0x2b0 fs/block_dev.c:1751 do_dentry_open+0x4b9/0x11b0 fs/open.c:817 do_open fs/namei.c:3252 [inline] path_openat+0x1b9a/0x2730 fs/namei.c:3369 do_filp_open+0x17e/0x3c0 fs/namei.c:3396 do_sys_openat2+0x16d/0x420 fs/open.c:1168 do_sys_open fs/open.c:1184 [inline] __do_sys_openat fs/open.c:1200 [inline] __se_sys_openat fs/open.c:1195 [inline] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1195 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Chain exists of: brd_devices_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(brd_devices_mutex); *** DEADLOCK *** 1 lock held by syz-executor.1/23213: #0: ffffffff8bac2ac8 (major_names_lock){+.+.}-{3:3}, at: request_gendisk_module block/genhd.c:970 [inline] #0: ffffffff8bac2ac8 (major_names_lock){+.+.}-{3:3}, at: get_gendisk+0x3c8/0x6a0 block/genhd.c:1023 stack backtrace: CPU: 1 PID: 23213 Comm: syz-executor.1 Not tainted 5.10.0-rc3-next-20201113-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+0x107/0x163 lib/dump_stack.c:120 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2115 check_prev_add kernel/locking/lockdep.c:2866 [inline] check_prevs_add kernel/locking/lockdep.c:2991 [inline] validate_chain kernel/locking/lockdep.c:3606 [inline] __lock_acquire+0x2ca6/0x5c00 kernel/locking/lockdep.c:4830 lock_acquire kernel/locking/lockdep.c:5435 [inline] lock_acquire+0x2a3/0x8c0 kernel/locking/lockdep.c:5400 __mutex_lock_common kernel/locking/mutex.c:956 [inline] __mutex_lock+0x134/0x1110 kernel/locking/mutex.c:1103 brd_probe+0x31/0x250 drivers/block/brd.c:434 request_gendisk_module block/genhd.c:973 [inline] get_gendisk+0x4c3/0x6a0 block/genhd.c:1023 bdev_get_gendisk fs/block_dev.c:1094 [inline] __blkdev_get+0x344/0x1870 fs/block_dev.c:1455 blkdev_get+0xd1/0x240 fs/block_dev.c:1634 blkdev_open+0x21d/0x2b0 fs/block_dev.c:1751 do_dentry_open+0x4b9/0x11b0 fs/open.c:817 do_open fs/namei.c:3252 [inline] path_openat+0x1b9a/0x2730 fs/namei.c:3369 do_filp_open+0x17e/0x3c0 fs/namei.c:3396 do_sys_openat2+0x16d/0x420 fs/open.c:1168 do_sys_open fs/open.c:1184 [inline] __do_sys_openat fs/open.c:1200 [inline] __se_sys_openat fs/open.c:1195 [inline] __x64_sys_openat+0x13f/0x1f0 fs/open.c:1195 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45deb9 Code: 0d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fc9e4533c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00000000000222c0 RCX: 000000000045deb9 RDX: 0000000000000000 RSI: 0000000020002040 RDI: ffffffffffffff9c RBP: 000000000118c010 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bfd4 R13: 00007ffd0970a31f R14: 00007fc9e45349c0 R15: 000000000118bfd4