syzbot


UBSAN: shift-out-of-bounds in exfat_fill_super

Status: upstream: reported on 2025/06/13 09:33
Reported-by: syzbot+6f326e692de8ac82d97f@syzkaller.appspotmail.com
First crash: 5d10h, last: 5d10h
Similar bugs (4)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream UBSAN: shift-out-of-bounds in exfat_fill_super (2) exfat 1 582d 578d 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 C error 3 1587d 1605d 20/29 fixed on 2021/04/09 19:46
android-5-15 UBSAN: shift-out-of-bounds in exfat_fill_super origin:lts C 4 4d09h 19d 0/2 upstream: reported C repro on 2025/05/30 13:08
android-6-1 UBSAN: shift-out-of-bounds in exfat_fill_super origin:upstream C 3 15d 63d 0/2 upstream: reported C repro on 2025/04/16 14:18

Sample crash report:
exFAT-fs (loop6): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
exFAT-fs (loop6): Medium has reported failures. Some data may be lost.
================================================================================
UBSAN: shift-out-of-bounds in fs/exfat/super.c:520:38
shift exponent 237 is too large for 32-bit type 'int'
CPU: 1 PID: 10196 Comm: syz.6.1161 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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
 exfat_read_boot_sector fs/exfat/super.c:520 [inline]
 __exfat_fill_super fs/exfat/super.c:576 [inline]
 exfat_fill_super+0x2943/0x2cf0 fs/exfat/super.c:644
 get_tree_bdev+0x3f1/0x610 fs/super.c:1325
 vfs_get_tree+0x88/0x270 fs/super.c:1530
 do_new_mount+0x24a/0xa40 fs/namespace.c:3010
 do_mount fs/namespace.c:3353 [inline]
 __do_sys_mount fs/namespace.c:3561 [inline]
 __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3538
 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: 0033:0x7f47718c60ca
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:00007f476f72be68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f476f72bef0 RCX: 00007f47718c60ca
RDX: 0000200000000100 RSI: 0000200000000240 RDI: 00007f476f72beb0
RBP: 0000200000000100 R08: 00007f476f72bef0 R09: 0000000000800000
R10: 0000000000800000 R11: 0000000000000246 R12: 0000200000000240
R13: 00007f476f72beb0 R14: 00000000000014fe R15: 0000200000000600
 </TASK>
================================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/13 09:32 linux-5.15.y 1c700860e8bc 98683f8f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan UBSAN: shift-out-of-bounds in exfat_fill_super
* Struck through repros no longer work on HEAD.