UBSAN: shift-out-of-bounds in exfat_fill_super

Status: upstream: reported C repro on 2025/05/30 13:08
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+967aa521d54edf6fb900@syzkaller.appspotmail.com
First crash: 437d, last: 12d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/05/30 lts (merge base) 98f47d0e9b8c C [report] UBSAN: shift-out-of-bounds in exfat_fill_super
2025/05/30 upstream (ToT) 8477ab143069 C Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream UBSAN: shift-out-of-bounds in exfat_fill_super (2) exfat -1 1 1000d 996d 0/29 auto-obsoleted due to no activity on 2024/02/22 05:01
upstream UBSAN: shift-out-of-bounds in exfat_fill_super exfat -1 syz, C error 3 2005d 2022d 20/29 fixed on 2021/04/09 19:46
linux-5.15 UBSAN: shift-out-of-bounds in exfat_fill_super (2) origin:lts-only -1 syz, C error 3 16d 322d 0/3 upstream: reported C repro on 2025/09/21 18:12
linux-5.15 UBSAN: shift-out-of-bounds in exfat_fill_super -1 1 423d 423d 0/3 auto-obsoleted due to no activity on 2025/09/21 09:33
android-6-1 UBSAN: shift-out-of-bounds in exfat_fill_super origin:upstream -1 syz, C error 15 19d 481d 0/2 upstream: reported C repro on 2025/04/16 14:18
▶ ▼ Last patch testing requests (8)
Created Duration User Patch Repo Result
2026/05/05 00:25 13m retest repro android13-5.15-lts report log
2026/05/05 00:25 13m retest repro android13-5.15-lts report log
2026/04/20 11:22 13m retest repro android13-5.15-lts report log
2026/04/05 06:36 6m retest repro android13-5.15-lts report log
2026/04/05 06:36 25m retest repro android13-5.15-lts report log
2026/03/22 05:26 5m retest repro android13-5.15-lts report log
2026/03/22 05:26 5m retest repro android13-5.15-lts report log
2026/03/22 05:26 6m retest repro android13-5.15-lts report log
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/07/28 23:04 2h01m bisect fix android13-5.15-lts OK (0) job log log
2025/08/14 22:50 1h31m bisect fix android13-5.15-lts OK (0) job log log
2025/07/15 17:50 1h13m bisect fix android13-5.15-lts OK (0) job log log

Sample crash report:
WARNING: The mand mount option has been deprecated and
         and is ignored by this kernel. Remove the mand
         option from the mount to silence this warning.
=======================================================
exFAT-fs (loop2): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
exFAT-fs (loop2): Medium has reported failures. Some data may be lost.
================================================================================
UBSAN: shift-out-of-bounds in fs/exfat/super.c:523:38
shift exponent 117 is too large for 32-bit type 'int'
CPU: 1 PID: 372 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+0x21/0x30 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
 exfat_read_boot_sector fs/exfat/super.c:523 [inline]
 __exfat_fill_super fs/exfat/super.c:579 [inline]
 exfat_fill_super+0x2921/0x2d20 fs/exfat/super.c:647
 get_tree_bdev+0x43f/0x690 fs/super.c:1325
 exfat_get_tree+0x1c/0x20 fs/exfat/super.c:719
 vfs_get_tree+0x89/0x260 fs/super.c:1530
 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: 0033:0x7f51145590ca
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:00007f51143b9e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f51143b9ee0 RCX: 00007f51145590ca
RDX: 00002000000005c0 RSI: 0000200000000240 RDI: 00007f51143b9ea0
RBP: 00002000000005c0 R08: 00007f51143b9ee0 R09: 0000000003010050
R10: 0000000003010050 R11: 0000000000000246 R12: 0000200000000240
R13: 00007f51143b9ea0 R14: 00000000000014fe R15: 0000200000000600
 </TASK>
================================================================================
exFAT-fs (loop2): unable to set blocksize 2097152
exFAT-fs (loop2): failed to read boot sector
exFAT-fs (loop2): failed to recognize exfat type

Crashes (21):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/28 09:51 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 exfat_fill_super
2026/05/27 04:46 android13-5.15-lts 8969ee93a483 2b01f00e .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 exfat_fill_super
2026/03/07 20:13 android13-5.15-lts f55534477be4 5cb44a80 .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 exfat_fill_super
2026/03/01 19:08 android13-5.15-lts e714749f59d3 43249bac .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 exfat_fill_super
2026/02/24 05:27 android13-5.15-lts 13d6d33696ef 41d2fa6a .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 exfat_fill_super
2025/12/14 05:38 android13-5.15-lts 057fdbf6d3c7 d6526ea3 .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 exfat_fill_super
2025/12/14 04:56 android13-5.15-lts 057fdbf6d3c7 d6526ea3 .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 exfat_fill_super
2025/10/27 00:23 android13-5.15-lts 1edb21e89ce4 c0460fcd .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 exfat_fill_super
2025/09/08 21:46 android13-5.15-lts 1cd26e1d9a89 d291dd2d .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-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/05/30 14:09 android13-5.15-lts 4032a894ccb2 3d2f584d .config strace 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 exfat_fill_super
2025/05/30 13:36 android13-5.15-lts 4032a894ccb2 3d2f584d .config strace 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 exfat_fill_super
2025/05/30 13:02 android13-5.15-lts 4032a894ccb2 3d2f584d .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 exfat_fill_super
2026/06/21 11:42 android13-5.15-lts b4be5dda13e9 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2026/06/16 06:15 android13-5.15-lts b4be5dda13e9 50bb0618 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2026/06/05 02:09 android13-5.15-lts 8969ee93a483 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/11/08 19:27 android13-5.15-lts 8a8f52308945 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/10/26 21:10 android13-5.15-lts 1edb21e89ce4 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/10/04 13:48 android13-5.15-lts 2bbc293701f8 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/09/15 15:56 android13-5.15-lts 8d934e0056f7 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/09/08 20:55 android13-5.15-lts 1cd26e1d9a89 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
2025/05/30 12:22 android13-5.15-lts 4032a894ccb2 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super
* Struck through repros no longer work on HEAD.