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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: 814d, last: 10h41m
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 C unreliable 88 1910d 1925d 19/29 fixed on 2021/03/10 01:48
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2026/03/18 13:21 6m retest repro android13-5.15-lts report log
2026/03/18 13:21 5m retest repro android13-5.15-lts report log
2026/03/18 13:21 8m retest repro android13-5.15-lts report log
2026/03/18 13:21 5m retest repro android13-5.15-lts report log
2026/02/28 02:47 9m retest repro android13-5.15-lts report log
2026/02/28 02:47 2h02m retest repro android13-5.15-lts report log
2026/02/28 02:47 2h00m retest repro android13-5.15-lts report log
2026/02/28 02:47 10m retest repro android13-5.15-lts report 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:
loop2: detected capacity change from 0 to 512
EXT4-fs: Warning: mounting with data=journal disables delayed allocation, dioread_nolock, O_DIRECT and fast_commit support!
EXT4-fs (loop2): encrypted files will use data=ordered instead of data journaling mode
================================================================================
UBSAN: shift-out-of-bounds in fs/ext4/super.c:4447:27
shift exponent 8192 is too large for 32-bit type 'int'
CPU: 0 PID: 393 Comm: syz.2.27 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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+0x37c/0x400 lib/ubsan.c:321
 ext4_fill_super+0x6a42/0x8bd0 fs/ext4/super.c:4447
 mount_bdev+0x2ae/0x3e0 fs/super.c:1400
 ext4_mount+0x34/0x40 fs/ext4/super.c:6648
 legacy_get_tree+0xed/0x190 fs/fs_context.c:611
 vfs_get_tree+0x89/0x260 fs/super.c:1530
 do_new_mount+0x25a/0xa20 fs/namespace.c:3034
 path_mount+0x659/0xff0 fs/namespace.c:3364
 do_mount fs/namespace.c:3377 [inline]
 __do_sys_mount fs/namespace.c:3585 [inline]
 __se_sys_mount+0x320/0x390 fs/namespace.c:3562
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3562
 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: 0033:0x7fd40d147a0a
Code: 48 c7 c2 e8 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd40cfa8e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fd40cfa8ee0 RCX: 00007fd40d147a0a
RDX: 0000200000000540 RSI: 00002000000001c0 RDI: 00007fd40cfa8ea0
RBP: 0000200000000540 R08: 00007fd40cfa8ee0 R09: 0000000000000088
R10: 0000000000000088 R11: 0000000000000246 R12: 00002000000001c0
R13: 00007fd40cfa8ea0 R14: 000000000000042f R15: 00002000000005c0
 </TASK>
================================================================================
EXT4-fs (loop2): bad geometry: first data block 0 is beyond end of filesystem (0)

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
* Struck through repros no longer work on HEAD.