UBSAN: shift-out-of-bounds in befs_check_sb

Status: upstream: reported C repro on 2023/07/28 00:42
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+affd78fff833c2695d02@syzkaller.appspotmail.com
First crash: 1104d, last: 35d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2023/12/30 upstream (ToT) f016f7547aee C [report] UBSAN: shift-out-of-bounds in befs_check_sb
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 UBSAN: shift-out-of-bounds in befs_check_sb origin:upstream -1 syz, C error 19 228d 1096d 0/3 upstream: reported C repro on 2023/08/05 00:55
linux-6.6 UBSAN: shift-out-of-bounds in befs_check_sb origin:upstream -1 syz, C error 3 228d 228d 0/2 upstream: reported C repro on 2025/12/19 17:02
upstream UBSAN: shift-out-of-bounds in befs_check_sb prio:high fs -1 syz, C error done 79 60d 1119d 0/29 upstream: reported C repro on 2023/07/12 13:47
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/06/30 13:15 1h50m retest repro linux-5.15.y report log
2026/06/30 13:15 1h45m retest repro linux-5.15.y report log
2026/06/30 13:15 15m retest repro linux-5.15.y report log
2026/03/28 11:17 10m retest repro linux-5.15.y error
2026/03/14 07:58 10m retest repro linux-5.15.y error
2026/03/14 07:58 5m retest repro linux-5.15.y error
2026/01/17 07:10 9m retest repro linux-5.15.y report log
2026/01/03 01:06 14m retest repro linux-5.15.y report log
2026/01/03 01:06 9m retest repro linux-5.15.y report log
2025/10/21 15:07 10m retest repro linux-5.15.y report log

Sample crash report:
loop0: detected capacity change from 0 to 128
================================================================================
UBSAN: shift-out-of-bounds in fs/befs/super.c:96:9
shift exponent 2066842816 is too large for 32-bit type 'int'
CPU: 0 PID: 4313 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 ubsan_epilogue+0xa/0x30 lib/ubsan.c:151
 __ubsan_handle_shift_out_of_bounds+0x37c/0x400 lib/ubsan.c:321
 befs_check_sb+0x40d/0x4b0 fs/befs/super.c:96
 befs_fill_super+0x8d9/0xe80 fs/befs/linuxvfs.c:874
 mount_bdev+0x287/0x3c0 fs/super.c:1400
 legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x24a/0xa40 fs/namespace.c:3025
 do_mount fs/namespace.c:3368 [inline]
 __do_sys_mount fs/namespace.c:3576 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3553
 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: 0033:0x7f51bd3e066a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe38a59048 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffe38a590d0 RCX: 00007f51bd3e066a
RDX: 0000200000000040 RSI: 0000200000000000 RDI: 00007ffe38a59090
RBP: 0000200000000040 R08: 00007ffe38a590d0 R09: 0000000000800001
R10: 0000000000800001 R11: 0000000000000246 R12: 0000200000000000
R13: 00007ffe38a59090 R14: 0000000000009e17 R15: 0000200000000080
 </TASK>
================================================================================

Crashes (16):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/23 02:40 linux-5.15.y 43bb85222e53 0ac7291c .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2023/12/30 18:35 linux-5.15.y d93fa2c78854 fb427a07 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2023/07/28 00:41 linux-5.15.y 09996673e313 92476829 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
2025/12/19 16:54 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2025/12/19 16:54 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2025/12/06 19:03 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2025/12/06 19:01 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2025/09/22 20:59 linux-5.15.y 43bb85222e53 0ac7291c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2025/09/22 20:28 linux-5.15.y 43bb85222e53 0ac7291c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2025/09/22 20:27 linux-5.15.y 43bb85222e53 0ac7291c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in befs_check_sb
2024/01/23 11:08 linux-5.15.y ddcaf4999061 1c0ecc51 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
2024/01/23 07:19 linux-5.15.y ddcaf4999061 1c0ecc51 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
2024/01/21 04:57 linux-5.15.y ddcaf4999061 9bd8dcda .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
2024/01/19 19:36 linux-5.15.y ddcaf4999061 9bd8dcda .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
2024/01/19 17:15 linux-5.15.y ddcaf4999061 9bd8dcda .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
2024/01/19 06:07 linux-5.15.y ddcaf4999061 21772ce4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 UBSAN: shift-out-of-bounds in befs_check_sb
* Struck through repros no longer work on HEAD.