UBSAN: shift-out-of-bounds in ext4_check_opt_consistency

Status: upstream: reported C repro on 2026/01/05 06:19
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+04b7043650d5edd3069b@syzkaller.appspotmail.com
First crash: 202d, last: 16d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/01/06 lts (merge base) f6e38ae624cf C [report] UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/01/06 upstream (ToT) 7f98ab9da046 C Didn't crash
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency -1 C error 4 98d 98d 0/3 upstream: reported C repro on 2026/04/19 15:50
▶ ▼ Last patch testing requests (7)
Created Duration User Patch Repo Result
2026/04/18 21:22 14m retest repro android14-6.1 report log
2026/04/18 21:22 34m retest repro android14-6.1 report log
2026/04/02 02:54 6m retest repro android14-6.1 report log
2026/04/02 02:54 7m retest repro android14-6.1 report log
2026/04/02 02:52 5m retest repro android14-6.1 report log
2026/02/28 20:10 8m retest repro android14-6.1 report log
2026/01/22 02:40 6m retest repro android14-6.1 report log

Sample crash report:
ext4 filesystem being mounted at /0/file1 supports timestamps until 2038-01-19 (0x7fffffff)
================================================================================
UBSAN: shift-out-of-bounds in fs/ext4/super.c:2756:15
shift exponent 1987084706 is too large for 32-bit type 'int'
CPU: 0 PID: 374 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 dump_stack+0x15/0x24 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_check_opt_consistency+0x1353/0x16e0 fs/ext4/super.c:2756
 ext4_reconfigure+0xc7/0x27b0 fs/ext4/super.c:6681
 reconfigure_super+0x233/0x8b0 fs/super.c:982
 do_remount fs/namespace.c:2742 [inline]
 path_mount+0xce4/0xfd0 fs/namespace.c:3403
 do_mount fs/namespace.c:3424 [inline]
 __do_sys_mount fs/namespace.c:3632 [inline]
 __se_sys_mount+0x320/0x390 fs/namespace.c:3609
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3609
 x64_sys_call+0x65d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9586f9de59
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:00007ffcc2bffff8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f9587225fa0 RCX: 00007f9586f9de59
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007f9587033e6f R08: 0000200000000000 R09: 0000000000000000
R10: 0000000002200020 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9587225fac R14: 00007f9587225fa0 R15: 00007f9587225fa0
 </TASK>
================================================================================
EXT4-fs: test_dummy_encryption requires encrypt feature

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/10 03:44 android14-6.1 52939c41021c 4167ee25 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (clean fs)] [mounted in repro #3 (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/07/10 03:26 android14-6.1 52939c41021c 4167ee25 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (clean fs)] [mounted in repro #3 (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/06/15 00:50 android14-6.1 f17c14b8ada7 1d2f3589 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] [mounted in repro #3 (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/04/04 09:03 android14-6.1 9ab204675a62 4440e7c2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/02/14 14:51 android14-6.1 edbe3e111301 1e62d198 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/01/05 07:07 android14-6.1 5e6db7045704 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/01/05 06:38 android14-6.1 5e6db7045704 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/01/05 06:09 android14-6.1 5e6db7045704 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/07/06 09:04 android14-6.1 cf4093a4ac64 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/06/18 04:03 android14-6.1 9f35ca3ff66c b62b3ded .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/06/07 23:19 android14-6.1 d73749230104 cc095639 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
2026/01/05 05:37 android14-6.1 5e6db7045704 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_check_opt_consistency
* Struck through repros no longer work on HEAD.