[Android 6.1] UBSAN: shift-out-of-bounds in exfat_fill_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: efda22f3484c ANDROID: GKI: update symbol list for xiaomi
git tree: android14-6.1
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11cd88cc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=82e71fa000d4b060
dashboard link: https://syzkaller.appspot.com/bug?extid=619a09223476d86149f7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11bd8204580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12d86fe4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/45fb6f318eae/disk-efda22f3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1777106bf339/vmlinux-efda22f3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2cf49227823a/bzImage-efda22f3.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/fc238772fba6/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=16bd8204580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+619a09...@syzkaller.appspotmail.com

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: 434 Comm: syz-executor268 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: 0033:0x7fa7fb0dcfea
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:00007fa7fb098088 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fa7fb0980a0 RCX: 00007fa7fb0dcfea
RDX: 0000200000000000 RSI: 0000200000000240 RDI: 00007fa7fb0980a0
RBP: 0000200000000240 R08: 00007fa7fb0980e0 R09: 00000000000014f8
R10: 0000000000000000 R11: 0000000000000286 R12: 0000200000000000
R13: 00007fa7fb0980e0 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


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