WARNING in btrfs_init_new_device

Status: upstream: reported C repro on 2026/08/04 19:58
Reported-by: syzbot+8fe9b646e3e054e4beed@syzkaller.appspotmail.com
First crash: 100d, last: 11d
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/09/27 upstream (ToT) [unknown] C Failed due to an error; will retry later
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in btrfs_init_new_device prio:normal btrfs -1 syz, C error 215 5d06h 95d 20/29 upstream: reported C repro on 2026/08/10 00:34
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/11/01 11:29 2h38m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
BTRFS warning (device loop0): creating sysfs device link for devid 2 failed: -17
------------[ cut here ]------------
WARNING: CPU: 1 PID: 4559 at fs/btrfs/volumes.c:2836 btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
Modules linked in:
CPU: 1 PID: 4559 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 62400005 (nZCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
lr : btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
sp : ffff8000212c7bd0
x29: ffff8000212c7c20 x28: ffff0000df5f0000 x27: 00000000ffffffef
x26: 1fffe0001c2d680a x25: dfff800000000000 x24: 0000000000000000
x23: 0000000000000000 x22: ffff0000d96fa800 x21: ffff0000efd75130
x20: ffff0000efd74000 x19: ffff0000c04b2c00 x18: 1fffe00033e7217e
x17: 0000000000000000 x16: ffff800011ba0e90 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00033e721a3 x12: 0000000000000000
x11: ff00800008195f68 x10: 0000000000000000 x9 : aa61fca031a40000
x8 : aa61fca031a40000 x7 : 0000000000000001 x6 : 0000000000000001
x5 : ffff8000212c7658 x4 : ffff800015484e80 x3 : ffff800008540dd8
x2 : 0000000000000001 x1 : 0000000100000000 x0 : 0000000000000000
Call trace:
 btrfs_init_new_device+0x1548/0x1980 fs/btrfs/volumes.c:2836
 btrfs_ioctl_add_dev+0x184/0x3b8 fs/btrfs/ioctl.c:3592
 btrfs_ioctl+0xa48/0xb38 fs/btrfs/ioctl.c:5545
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 324
hardirqs last  enabled at (323): [<ffff8000083138a0>] __up_console_sem+0xb4/0xfc kernel/printk/printk.c:261
hardirqs last disabled at (324): [<ffff800011b9d0cc>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (280): [<ffff8000081ae3b4>] softirq_handle_end kernel/softirq.c:439 [inline]
softirqs last  enabled at (280): [<ffff8000081ae3b4>] handle_softirqs+0xb1c/0xc90 kernel/softirq.c:624
softirqs last disabled at (155): [<ffff800008020e6c>] __do_softirq+0x14/0x20 kernel/softirq.c:630
---[ end trace 0000000000000000 ]---
BTRFS: error (device loop0: state A) in btrfs_init_new_device:2836: errno=-17 Object already exists
BTRFS info (device loop0: state EA): forced readonly

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/10 10:15 linux-6.1.y cf82dcca9634 4e8b1cc6 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-6-1-kasan-arm64 WARNING in btrfs_init_new_device
2026/09/10 09:33 linux-6.1.y cf82dcca9634 4e8b1cc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in btrfs_init_new_device
2026/08/04 19:58 linux-6.1.y fb28aa725e05 d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 WARNING in btrfs_init_new_device
* Struck through repros no longer work on HEAD.