UBSAN: shift-out-of-bounds in ufs_fill_super

Status: upstream: reported on 2026/08/06 15:25
Subsystems: fs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+5585f47221c0de04168d@syzkaller.appspotmail.com
First crash: 6d06h, last: 5d11h
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ID Workflow Result Correct Bug Created Started Finished Revision
9c828e11 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ UBSAN: shift-out-of-bounds in ufs_fill_super 2026/08/09 07:57 2026/08/09 07:57 2026/08/09 08:44 5d63f80b
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Title Replies (including bot) Last reply
[syzbot] [fs?] UBSAN: shift-out-of-bounds in ufs_fill_super 0 (1) 2026/08/06 15:25
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 UBSAN: shift-out-of-bounds in ufs_fill_super -1 syz, C 4 1d02h 5d20h 0/2 upstream: reported C repro on 2026/08/04 22:49

Sample crash report:
loop0: detected capacity change from 0 to 128
ufs: ufs_fill_super(): fs needs fsck
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/ufs/super.c:1177:18
shift exponent 4294967294 is too large for 32-bit type 'int'
CPU: 0 UID: 0 PID: 5327 Comm: syz.0.0 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:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494
 ufs_fill_super+0x5f8d/0x67e0 fs/ufs/super.c:1177
 get_tree_bdev_flags+0x430/0x4f0 fs/super.c:1640
 vfs_get_tree+0x92/0x2a0 fs/super.c:1700
 fc_mount fs/namespace.c:1198 [inline]
 do_new_mount_fc fs/namespace.c:3765 [inline]
 do_new_mount+0x319/0xdc0 fs/namespace.c:3841
 do_mount fs/namespace.c:4174 [inline]
 __do_sys_mount fs/namespace.c:4390 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4367
 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: 0033:0x7f6c6519e019
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:00007f6c66037fe8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f6c65425fa0 RCX: 00007f6c6519e019
RDX: 0000200000004000 RSI: 0000200000003000 RDI: 0000200000000040
RBP: 00007f6c6523500c R08: 0000200000005000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6c65426038 R14: 00007f6c65425fa0 R15: 00007ffd05bb6728
 </TASK>
---[ end trace ]---

Crashes (25):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/05 08:02 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:02 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:02 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:02 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:01 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:01 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:01 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/05 08:01 upstream 562bfb501c54 52aa2820 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 21:49 upstream 562bfb501c54 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 21:49 upstream 562bfb501c54 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:35 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:35 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:35 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:35 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:25 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:25 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:10 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:09 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:06 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:06 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:06 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 13:06 upstream 848acc8ffe1b 3c5eaa21 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 16:30 upstream 848acc8ffe1b 3c5eaa21 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 16:17 upstream 848acc8ffe1b 3c5eaa21 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 UBSAN: shift-out-of-bounds in ufs_fill_super
2026/08/04 16:15 upstream 848acc8ffe1b 3c5eaa21 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 UBSAN: shift-out-of-bounds in ufs_fill_super
* Struck through repros no longer work on HEAD.