syzbot


WARNING in super_dev_register

Status: upstream: reported C repro on 2026/07/03 00:59
Subsystems: fuse
Labels: prio:normal
[Documentation on labels]
Reported-by: syzbot+72fe3ea5814121fbc76e@syzkaller.appspotmail.com
Fix commit: block: reject block device inodes with i_rdev == 0 in lookup_bdev()
Patched on: [ci-upstream-linux-next-kasan-gce-root ci-upstream-rust-kasan-gce], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 13d, last: 10d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
a1908e2d-63f6-4f32-9299-9b9991e34971 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in super_dev_register 2026/07/03 00:00 2026/07/03 00:00 2026/07/03 00:58 93f579545ae410f5bccfa141d2e7bf03178f036c

			
		
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] block: reject block device inodes with i_rdev == 0 in lookup_bdev() 1 (1) 2026/07/03 06:55
[syzbot] [fuse?] WARNING in super_dev_register 0 (1) 2026/07/03 00:59

Sample crash report:
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
------------[ cut here ]------------
!sb->s_dev
WARNING: fs/super.c:509 at super_dev_register+0xf8/0x250 fs/super.c:509, CPU#1: syz.0.17/5906
Modules linked in:
CPU: 1 UID: 0 PID: 5906 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:super_dev_register+0xf8/0x250 fs/super.c:509
Code: 04 38 84 c0 0f 85 34 01 00 00 8b 2b 31 ff 89 ee e8 9d 2a 85 ff 85 ed 0f 85 98 00 00 00 e8 e0 25 85 ff eb 17 e8 d9 25 85 ff 90 <0f> 0b 90 48 85 db 75 c4 e8 cb 25 85 ff 90 0f 0b 90 43 0f b6 04 3c
RSP: 0018:ffffc90003f3f9d0 EFLAGS: 00010293
RAX: ffffffff82401307 RBX: ffff888032be2000 RCX: ffff88802d478000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff82401d10 R12: 1ffff11007997402
R13: dffffc0000000000 R14: ffff88803ccba010 R15: dffffc0000000000
FS:  0000555563c9e500(0000) GS:ffff888125b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000003000 CR3: 00000000505ae000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 sget_fc+0x12f6/0x1a60 fs/super.c:896
 sget_dev fs/super.c:1480 [inline]
 get_tree_bdev_flags+0x212/0x4f0 fs/super.c:1867
 fuse_get_tree+0x194/0x3b0 fs/fuse/inode.c:1877
 vfs_get_tree+0x92/0x2a0 fs/super.c:1941
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3777 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3853
 do_mount fs/namespace.c:4186 [inline]
 __do_sys_mount fs/namespace.c:4402 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4379
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2ea523de59
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:00007ffebb4997a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f2ea54c5fa0 RCX: 00007f2ea523de59
RDX: 0000200000000080 RSI: 00002000000000c0 RDI: 00002000000001c0
RBP: 00007f2ea52d3e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2ea54c5fac R14: 00007f2ea54c5fa0 R15: 00007f2ea54c5fa0
 </TASK>

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/03 00:21 linux-next 6eb8711ece2c 2b70b115 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/02 23:36 linux-next 6eb8711ece2c 2b70b115 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/02 22:45 linux-next 6eb8711ece2c 2b70b115 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/02 21:56 linux-next 6eb8711ece2c 2b70b115 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/06 01:17 linux-next 2b763db0c276 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in super_dev_register
2026/07/03 19:29 linux-next 2b763db0c276 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/03 19:29 linux-next 2b763db0c276 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/03 06:28 linux-next 6eb8711ece2c 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/03 01:49 linux-next 6eb8711ece2c 58bf2096 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
2026/07/02 19:55 linux-next 6eb8711ece2c 2b70b115 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in super_dev_register
* Struck through repros no longer work on HEAD.