syzbot


UBSAN: shift-out-of-bounds in exfat_fill_super

Status: upstream: reported C repro on 2025/04/16 14:18
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+619a09223476d86149f7@syzkaller.appspotmail.com
First crash: 2d19h, last: 2d18h
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
2025/04/16 upstream (ToT) c62f4b82d571 C Failed due to an error; will retry later
Similar bugs (2)
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 522d 518d 0/28 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 1527d 1544d 20/28 fixed on 2021/04/09 19:46

Sample crash report:
loop0: detected capacity change from 0 to 256
exFAT-fs (loop0): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
exFAT-fs (loop0): Medium has reported failures. Some data may be lost.
================================================================================
UBSAN: shift-out-of-bounds in fs/exfat/super.c:529:38
shift exponent 185 is too large for 32-bit type 'int'
CPU: 0 PID: 856 Comm: syz-executor634 Not tainted 6.1.129-syzkaller-00006-gefda22f3484c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 dump_stack+0x15/0x18 lib/dump_stack.c:113
 ubsan_epilogue lib/ubsan.c:151 [inline]
 __ubsan_handle_shift_out_of_bounds+0x3e1/0x440 lib/ubsan.c:321
 exfat_read_boot_sector fs/exfat/super.c:529 [inline]
 __exfat_fill_super fs/exfat/super.c:585 [inline]
 exfat_fill_super+0x2b3a/0x2b80 fs/exfat/super.c:649
 get_tree_bdev+0x440/0x680 fs/super.c:1368
 exfat_get_tree+0x1c/0x20 fs/exfat/super.c:721
 vfs_get_tree+0x88/0x290 fs/super.c:1575
 do_new_mount+0x2ba/0xb30 fs/namespace.c:3056
 path_mount+0x671/0x1070 fs/namespace.c:3386
 do_mount fs/namespace.c:3399 [inline]
 __do_sys_mount fs/namespace.c:3607 [inline]
 __se_sys_mount+0x2c4/0x3b0 fs/namespace.c:3584
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3584
 x64_sys_call+0x49d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9ba448b56a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9ba4445fd8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f9ba4445ff0 RCX: 00007f9ba448b56a
RDX: 0000200000000000 RSI: 0000200000000240 RDI: 00007f9ba4445ff0
RBP: 0000200000000240 R08: 00007f9ba4446030 R09: 00000000000014f8
R10: 0000000000000000 R11: 0000000000000286 R12: 0000200000000000
R13: 00007f9ba4446030 R14: 0000000000000003 R15: 0000000000000000
 </TASK>
================================================================================
exFAT-fs (loop0): unable to set blocksize 33554432
exFAT-fs (loop0): failed to read boot sector
exFAT-fs (loop0): failed to recognize exfat type

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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
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.