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Wed, 28 Oct 2026 22:12:29 -0700 (PDT) Date: Wed, 28 Oct 2026 22:12:29 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ae2d5bd.84012103.26b497.074c.GAE@google.com> Subject: [syzbot] [block?] possible deadlock in blkdev_write_iter From: syzbot To: axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 330517c63aa9 Merge tag 'char-misc-7.4-rc1' of git://git.ke.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=11962aa5580000 kernel config: https://syzkaller.appspot.com/x/.config?x=b03c85f3988bfcd5 dashboard link: https://syzkaller.appspot.com/bug?extid=39e465d3f7a1555b0f96 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16949aa5580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=105c53cd580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-330517c6.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/ecb230491807/vmlinux-330517c6.xz kernel image: https://storage.googleapis.com/syzbot-assets/ace3132a7acc/bzImage-330517c6.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+39e465d3f7a1555b0f96@syzkaller.appspotmail.com ============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- syz.2.64/6167 is trying to acquire lock: ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline] ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_buffered_write block/fops.c:734 [inline] ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_write_iter+0xd12/0x11d0 block/fops.c:812 but task is already holding lock: ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline] ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_write_iter+0xc5e/0x11d0 block/fops.c:811 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&sb->s_type->i_mutex_key#9); lock(&sb->s_type->i_mutex_key#9); *** DEADLOCK *** May be due to missing lock nesting notation locks held by syz.2.64/6167: 1, last CPU#2: #0: ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1039 [inline] #0: ffff88802a5f1ee8 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: blkdev_write_iter+0xc5e/0x11d0 block/fops.c:811 stack backtrace: CPU: 2 UID: 0 PID: 6167 Comm: syz.2.64 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_deadlock_bug.cold+0xbd/0xca kernel/locking/lockdep.c:3085 check_deadlock kernel/locking/lockdep.c:3137 [inline] validate_chain kernel/locking/lockdep.c:3939 [inline] __lock_acquire+0x13f4/0x1f40 kernel/locking/lockdep.c:5288 lock_acquire kernel/locking/lockdep.c:5942 [inline] lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899 down_read+0x94/0x4c0 kernel/locking/rwsem.c:1574 inode_lock_shared include/linux/fs.h:1039 [inline] blkdev_buffered_write block/fops.c:734 [inline] blkdev_write_iter+0xd12/0x11d0 block/fops.c:812 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x6af/0x1050 fs/read_write.c:687 ksys_write+0x12a/0x250 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f835bf9f559 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd15ca3258 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f835c225fa0 RCX: 00007f835bf9f559 RDX: 00000000fffffe38 RSI: 0000200000001140 RDI: 0000000000000004 RBP: 00007f835c036b20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f835c225fac R14: 00007f835c225fa0 R15: 00007f835c225fa0 --- 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@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup