UBSAN: shift-out-of-bounds in exfat_fill_super

Status: upstream: reported C repro on 2025/04/16 14:18
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+619a09223476d86149f7@syzkaller.appspotmail.com
First crash: 463d, last: 1d14h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/04/16 lts (merge base) 3a8358583626 C [report] UBSAN: shift-out-of-bounds in exfat_fill_super
2025/05/01 upstream (ToT) 4f79eaa2ceac C [report] UBSAN: shift-out-of-bounds in exfat_fill_super
▶ ▼ 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 982d 978d 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 C error 3 1987d 2004d 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 C error 3 56d 304d 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 405d 405d 0/3 auto-obsoleted due to no activity on 2025/09/21 09:33
android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super origin:lts -1 C 21 25d 419d 0/2 upstream: reported C repro on 2025/05/30 13:08
▶ ▼ Last patch testing requests (9)
Created Duration User Patch Repo Result
2026/07/11 10:15 15m retest repro android14-6.1 log
2026/07/11 10:15 14m retest repro android14-6.1 log
2026/07/11 10:15 13m retest repro android14-6.1 log
2026/07/11 10:15 16m retest repro android14-6.1 log
2026/07/11 10:15 13m retest repro android14-6.1 log
2026/06/02 19:52 16m retest repro android14-6.1 log
2026/06/02 19:52 14m retest repro android14-6.1 log
2026/06/02 19:52 15m retest repro android14-6.1 log
2025/11/13 07:03 51m junjie.cao@intel.com https://github.com/Junjie650/linux.git exfat-ubsan-guard report log
▶ ▼ Fix bisection attempts (5)
Created Duration User Patch Repo Result
2026/05/21 23:23 19m bisect fix android14-6.1 error job log
2025/09/24 00:23 1h16m bisect fix android14-6.1 OK (0) job log log
2025/08/20 17:00 1h11m bisect fix android14-6.1 OK (0) job log log
2025/07/05 11:15 2h44m bisect fix android14-6.1 OK (0) job log log
2025/06/03 04:35 54m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
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:532:38
shift exponent 117 is too large for 32-bit type 'int'
CPU: 0 PID: 461 Comm: syz.2.46 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
 exfat_read_boot_sector fs/exfat/super.c:532 [inline]
 __exfat_fill_super fs/exfat/super.c:588 [inline]
 exfat_fill_super+0x2856/0x2c70 fs/exfat/super.c:652
 get_tree_bdev+0x450/0x6a0 fs/super.c:1371
 exfat_get_tree+0x1c/0x20 fs/exfat/super.c:724
 vfs_get_tree+0x9a/0x270 fs/super.c:1578
 do_new_mount+0x251/0xb40 fs/namespace.c:3081
 path_mount+0x640/0xfd0 fs/namespace.c:3411
 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: 0033:0x7f310759f10a
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:00007f310840fe58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f310840fee0 RCX: 00007f310759f10a
RDX: 00002000000005c0 RSI: 0000200000000240 RDI: 00007f310840fea0
RBP: 00002000000005c0 R08: 00007f310840fee0 R09: 0000000003010050
R10: 0000000003010050 R11: 0000000000000246 R12: 0000200000000240
R13: 00007f310840fea0 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 (15):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/22 02:31 android14-6.1 72b456bf57ad b561ce9c .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 exfat_fill_super
2026/06/15 03:24 android14-6.1 f17c14b8ada7 1d2f3589 .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 exfat_fill_super
2026/03/10 09:45 android14-6.1 5afccbb9b4d4 6972f302 .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 exfat_fill_super
2026/03/08 00:10 android14-6.1 6bfa51973214 5cb44a80 .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 exfat_fill_super
2026/03/03 17:34 android14-6.1 6bfa51973214 4180d919 .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 exfat_fill_super
2025/12/31 17:52 android14-6.1 5e6db7045704 d6526ea3 .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 exfat_fill_super
2025/12/31 16:54 android14-6.1 5e6db7045704 d6526ea3 .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 exfat_fill_super
2025/12/28 09:12 android14-6.1 5e6db7045704 d6526ea3 .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 exfat_fill_super
2025/12/28 08:31 android14-6.1 5e6db7045704 d6526ea3 .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 exfat_fill_super
2025/11/09 02:09 android14-6.1 50ba6c46f3ac 4e1406b4 .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 exfat_fill_super
2025/11/09 01:49 android14-6.1 50ba6c46f3ac 4e1406b4 .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 exfat_fill_super
2025/04/16 14:39 android14-6.1 efda22f3484c a95239b1 .config strace 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 exfat_fill_super
2025/04/16 14:12 android14-6.1 efda22f3484c a95239b1 .config strace 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 exfat_fill_super
2026/06/07 09:09 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 exfat_fill_super
2025/04/16 13:43 android14-6.1 efda22f3484c a95239b1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 UBSAN: shift-out-of-bounds in exfat_fill_super
* Struck through repros no longer work on HEAD.