UBSAN: shift-out-of-bounds in ext4_fill_super

Status: upstream: reported C repro on 2023/12/25 17:58
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+f358aa23cf81d2593253@syzkaller.appspotmail.com
First crash: 1037d, last: 9d09h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2023/12/25 lts (merge base) 9b91d36ba301 C [report] UBSAN: shift-out-of-bounds in ext4_fill_super
2023/12/25 upstream (ToT) 861deac3b092 C [report] UBSAN: shift-out-of-bounds in ext4_handle_clustersize
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream UBSAN: shift-out-of-bounds in ext4_fill_super ext4 -1 syz, C unreliable 88 2133d 2149d 19/29 fixed on 2021/03/10 01:48
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2026/10/12 16:15 14m retest repro android13-5.15-lts report job log log
2026/10/12 16:15 10m retest repro android13-5.15-lts report job log log
2026/09/14 15:45 7m retest repro android13-5.15-lts report job log log
2026/09/14 15:45 6m retest repro android13-5.15-lts report job log log
2026/09/14 15:45 16m retest repro android13-5.15-lts report job log log
2026/09/14 15:45 6m retest repro android13-5.15-lts report job log log
2026/09/14 15:45 33m retest repro android13-5.15-lts report job log log
2026/08/18 16:50 6m retest repro android13-5.15-lts report job log log
▶ ▼ Fix bisection attempts (8)
Created Duration User Patch Repo Result
2024/10/15 00:25 0m bisect fix android13-5.15-lts error job log
2024/09/04 22:06 52m bisect fix android13-5.15-lts OK (0) job log log
2024/08/01 10:10 37m bisect fix android13-5.15-lts OK (0) job log log
2024/06/24 20:27 58m bisect fix android13-5.15-lts OK (0) job log log
2024/05/16 20:27 35m bisect fix android13-5.15-lts OK (0) job log log
2024/04/12 21:32 2h01m bisect fix android13-5.15-lts OK (0) job log log
2024/03/10 18:42 34m bisect fix android13-5.15-lts OK (0) job log log
2024/02/09 14:26 37m bisect fix android13-5.15-lts OK (0) job log log

Sample crash report:
EXT4-fs (loop0): Ignoring removed oldalloc option
================================================================================
UBSAN: shift-out-of-bounds in fs/ext4/super.c:4452:27
shift exponent 8192 is too large for 32-bit type 'int'
CPU: 0 PID: 305 Comm: syz-executor134 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 dump_stack+0x15/0x20 lib/dump_stack.c:113
 ubsan_epilogue+0xe/0x40 lib/ubsan.c:151
 __ubsan_handle_shift_out_of_bounds+0x364/0x3f0 lib/ubsan.c:321
 ext4_fill_super+0x6a7b/0x8bf0 fs/ext4/super.c:4452
 mount_bdev+0x28d/0x3c0 fs/super.c:1411
 ext4_mount+0x34/0x40 fs/ext4/super.c:6650
 legacy_get_tree+0xed/0x190 fs/fs_context.c:611
 vfs_get_tree+0x89/0x260 fs/super.c:1541
 do_new_mount+0x251/0xb40 fs/namespace.c:3037
 path_mount+0x640/0xff0 fs/namespace.c:3367
 do_mount fs/namespace.c:3380 [inline]
 __do_sys_mount fs/namespace.c:3588 [inline]
 __se_sys_mount+0x320/0x390 fs/namespace.c:3565
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3565
 x64_sys_call+0x6bf/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f740259a04a
Code: 48 c7 c2 d0 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 d0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f740256cfd8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f740256cff0 RCX: 00007f740259a04a
RDX: 00002000000005c0 RSI: 0000200000000600 RDI: 00007f740256cff0
RBP: 00002000000005c0 R08: 00007f740256d030 R09: 0000000000000000
R10: 0000000000010000 R11: 0000000000000206 R12: 0000200000000600
R13: 00007f740256d030 R14: 0000000000000003 R15: 0000000000010000
 </TASK>
================================================================================
EXT4-fs (loop0): bad geometry: block count 8192 exceeds size of device (256 blocks)

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/19 01:50 android13-5.15-lts ff23d765b06f 432c0077 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/06/27 00:22 android13-5.15-lts c85054db4618 fb92f11c .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/05/12 01:36 android13-5.15-lts 5628bb722180 d168f260 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/03/04 10:07 android13-5.15-lts e714749f59d3 4180d919 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/02/14 01:23 android13-5.15-lts 13d6d33696ef 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/02/13 20:44 android13-5.15-lts 13d6d33696ef 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/02/01 18:41 android13-5.15-lts 7e1070528954 6b8752f2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/02/01 12:25 android13-5.15-lts 7e1070528954 6b8752f2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/02/01 11:56 android13-5.15-lts 7e1070528954 6b8752f2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2025/09/22 17:11 android13-5.15-lts 8d934e0056f7 0ac7291c .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2025/03/15 23:27 android13-5.15-lts 7d1f9b5c2ff5 e2826670 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2025/01/08 15:19 android13-5.15-lts 19092c8155b4 f3558dbf .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2023/12/25 17:57 android13-5.15-lts 28e3f5851a99 fb427a07 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
2026/09/28 00:36 android13-5.15-lts 776976664f31 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in ext4_fill_super
* Struck through repros no longer work on HEAD.