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UBSAN: shift-out-of-bounds in ext4_handle_clustersize

Status: upstream: reported C repro on 2023/12/24 13:33
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+30f90bc7bfdd0cdba283@syzkaller.appspotmail.com
First crash: 798d, last: 10d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2023/12/24 lts (merge base) 082280fe94a0 C [report] UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2023/12/24 upstream (ToT) 861deac3b092 C [report] UBSAN: shift-out-of-bounds in ext4_handle_clustersize
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream UBSAN: shift-out-of-bounds in ext4_handle_clustersize (2) ext4 -1 C error done 3 795d 799d 25/29 fixed on 2024/02/02 11:15
upstream UBSAN: shift-out-of-bounds in ext4_handle_clustersize ext4 -1 2 967d 983d 0/29 auto-obsoleted due to no activity on 2023/10/16 19:25
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2025/12/21 12:12 6m retest repro android14-6.1 report log
2025/10/12 01:08 6m retest repro android14-6.1 report log
▶ ▼ Fix bisection attempts (14)
Created Duration User Patch Repo Result
2025/05/23 00:05 2h00m bisect fix android14-6.1 error job log
2025/04/20 01:48 48m bisect fix android14-6.1 OK (0) job log log
2025/03/16 21:43 1h52m bisect fix android14-6.1 OK (0) job log log
2025/02/12 22:46 2h01m bisect fix android14-6.1 OK (0) job log log
2025/01/12 01:23 1h36m bisect fix android14-6.1 OK (0) job log log
2024/11/23 02:18 1h44m bisect fix android14-6.1 OK (0) job log log
2024/10/19 06:59 2h11m bisect fix android14-6.1 OK (0) job log log
2024/09/17 18:34 44m bisect fix android14-6.1 OK (0) job log log
2024/08/13 23:37 1h23m bisect fix android14-6.1 OK (0) job log log
2024/07/03 10:19 1h50m bisect fix android14-6.1 OK (0) job log log
2024/05/25 13:10 54m bisect fix android14-6.1 OK (0) job log log
2024/04/20 21:26 1h07m bisect fix android14-6.1 OK (0) job log log
2024/03/19 02:00 55m bisect fix android14-6.1 OK (0) job log log
2024/02/17 01:23 1h01m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
EXT4-fs: Ignoring removed nobh option
EXT4-fs: Warning: mounting with an experimental mount option 'dioread_nolock' for blocksize < PAGE_SIZE
================================================================================
UBSAN: shift-out-of-bounds in fs/ext4/super.c:4345:27
shift exponent 2786239568 is too large for 32-bit type 'int'
CPU: 0 PID: 726 Comm: syz.2.132 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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+0x37c/0x400 lib/ubsan.c:321
 ext4_handle_clustersize+0x4b3/0x5c0 fs/ext4/super.c:4345
 __ext4_fill_super fs/ext4/super.c:5203 [inline]
 ext4_fill_super+0x3fa3/0x7a40 fs/ext4/super.c:5650
 get_tree_bdev+0x447/0x690 fs/super.c:1368
 ext4_get_tree+0x1c/0x20 fs/ext4/super.c:5680
 vfs_get_tree+0x9a/0x270 fs/super.c:1575
 do_new_mount+0x25a/0xa20 fs/namespace.c:3078
 path_mount+0x659/0xfc0 fs/namespace.c:3408
 do_mount fs/namespace.c:3421 [inline]
 __do_sys_mount fs/namespace.c:3629 [inline]
 __se_sys_mount+0x320/0x390 fs/namespace.c:3606
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3606
 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: 0033:0x7f2cbb99d8ca
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:00007f2cbc853e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f2cbc853ee0 RCX: 00007f2cbb99d8ca
RDX: 0000200000000040 RSI: 0000200000000000 RDI: 00007f2cbc853ea0
RBP: 0000200000000040 R08: 00007f2cbc853ee0 R09: 0000000000010000
R10: 0000000000010000 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f2cbc853ea0 R14: 00000000000004cd R15: 0000200000000140
 </TASK>
================================================================================
EXT4-fs (loop2): fragment/cluster size (67108864) != block size (1024)

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/19 01:30 android14-6.1 edbe3e111301 77d4d919 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2026/02/19 00:22 android14-6.1 edbe3e111301 77d4d919 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2026/02/18 20:41 android14-6.1 edbe3e111301 77d4d919 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2026/02/07 02:31 android14-6.1 c9e2710a7bd0 f20fc9f9 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2026/02/06 20:32 android14-6.1 c9e2710a7bd0 97745f52 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2026/02/06 20:05 android14-6.1 c9e2710a7bd0 97745f52 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
2023/12/24 13:31 android14-6.1 401a2769d990 fb427a07 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 UBSAN: shift-out-of-bounds in ext4_handle_clustersize
* Struck through repros no longer work on HEAD.