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Fri, 06 Nov 2026 09:52:53 -0800 (PST) Date: Fri, 06 Nov 2026 09:52:53 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6aee13f5.02d3f859.2829d1.0014.GAE@google.com> Subject: [syzbot] [block?] WARNING in bd_unlink_disk_holder 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: b0958b1397fb arm64: mm: validate /dev/mem mmap ranges with.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci console output: https://syzkaller.appspot.com/x/log.txt?x=1018bddd580000 kernel config: https://syzkaller.appspot.com/x/.config?x=a58b6b4d667e7a61 dashboard link: https://syzkaller.appspot.com/bug?extid=0a8119ab801b078213ea compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 userspace arch: arm64 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1418bddd580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/a1caa79f24c0/disk-b0958b13.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/99b068dd4197/vmlinux-b0958b13.xz kernel image: https://storage.googleapis.com/syzbot-assets/e135f96e545e/Image-b0958b13.gz.xz AI-generated root cause summary: In drivers/md/md.c:bind_rdev_to_array(), an rdev is added to mddev->disks and bd_link_disk_holder() is called to create the holder/slave relationship without checking its return value. If bd_link_disk_holder() fails (for example, returning -EINVAL when an array's own block device or partition is imported into itself, or on memory/sysfs failures), no bd_holder_disk entry is added to disk->slave_bdevs, yet the device remains bound to the array. When the array is subsequently stopped via do_md_stop() -> export_array() -> md_kick_rdev_from_array(), bd_unlink_disk_holder() is called and bd_find_holder_disk() returns NULL, triggering WARN_ON_ONCE(holder == NULL) at block/holder.c:147. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=0a8119ab801b078213ea IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0a8119ab801b078213ea@syzkaller.appspotmail.com md: md4 stopped. ------------[ cut here ]------------ WARNING: block/holder.c:147 at bd_find_holder_disk block/holder.c:18 [inline], CPU#0: syz.4.21/5133 WARNING: block/holder.c:147 at bd_unlink_disk_holder+0xd8/0x2d4 block/holder.c:146, CPU#0: syz.4.21/5133 Modules linked in: CPU: 0 UID: 0 PID: 5133 Comm: syz.4.21 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026 pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : bd_unlink_disk_holder+0xd8/0x2d4 block/holder.c:18 lr : bd_find_holder_disk block/holder.c:18 [inline] lr : bd_unlink_disk_holder+0xd8/0x2d4 block/holder.c:146 sp : ffff800098f877e0 x29: ffff800098f877e0 x28: 1fffe000192c2f06 x27: ffff0000d92043d0 x26: 1fffe00018291306 x25: 1fffe0001b240879 x24: ffff0000d92043c8 x23: dfff800000000000 x22: ffff0000c1489830 x21: ffff0000c1489700 x20: ffff0000d9204000 x19: ffff0000d92043d0 x18: 1fffe000359cf228 x17: 0000000000000003 x16: ffff8000898b7000 x15: ffff80008996b2a0 x14: 00000000005a60a9 x13: 0000000000000001 x12: 0000000000000003 x11: 0000000000000000 x10: 0000000000000001 x9 : 0000000000000000 x8 : 0000000000000000 x7 : ffff8000818fb144 x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff80008046bc7c x2 : 0000000000000001 x1 : ffff0000d96b0000 x0 : 0000000000000000 Call trace: bd_find_holder_disk block/holder.c:18 [inline] (P) bd_unlink_disk_holder+0xd8/0x2d4 block/holder.c:146 (P) md_kick_rdev_from_array+0x8c/0x324 drivers/md/md.c:2683 export_array drivers/md/md.c:2714 [inline] do_md_stop+0x708/0xe6c drivers/md/md.c:7252 md_ioctl+0x14ec/0x23e4 drivers/md/md.c:8462 blkdev_ioctl+0x574/0x904 block/ioctl.c:798 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __arm64_sys_ioctl+0x154/0x1cc fs/ioctl.c:583 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:796 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:815 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 irq event stamp: 2038 hardirqs last enabled at (2037): [] vprintk_store+0x924/0xb94 kernel/printk/printk.c:2385 hardirqs last disabled at (2038): [] el1_brk64+0x20/0x54 arch/arm64/kernel/entry-common.c:483 softirqs last enabled at (1948): [] local_bh_enable include/linux/bottom_half.h:33 [inline] softirqs last enabled at (1948): [] put_cpu_fpsimd_context arch/arm64/kernel/fpsimd.c:251 [inline] softirqs last enabled at (1948): [] do_sve_acc+0x3ac/0x56c arch/arm64/kernel/fpsimd.c:1333 softirqs last disabled at (1946): [] local_bh_disable include/linux/bottom_half.h:20 [inline] softirqs last disabled at (1946): [] get_cpu_fpsimd_context arch/arm64/kernel/fpsimd.c:234 [inline] softirqs last disabled at (1946): [] do_sve_acc+0x104/0x56c arch/arm64/kernel/fpsimd.c:1308 ---[ end trace 0000000000000000 ]--- --- 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