syzbot

loop2: detected capacity change from 0 to 256
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.
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UBSAN: shift-out-of-bounds in fs/exfat/super.c:529:38
shift exponent 121 is too large for 32-bit type 'int'
CPU: 1 PID: 388 Comm: syz.2.21 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 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+0x37c/0x400 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+0x27e9/0x2bb0 fs/exfat/super.c:649
 get_tree_bdev+0x444/0x680 fs/super.c:1368
 exfat_get_tree+0x1c/0x20 fs/exfat/super.c:721
 vfs_get_tree+0x9a/0x270 fs/super.c:1575
 do_new_mount+0x25a/0xa20 fs/namespace.c:3078
 path_mount+0x675/0x1010 fs/namespace.c:3408
 do_mount fs/namespace.c:3421 [inline]
 __do_sys_mount fs/namespace.c:3629 [inline]
 __se_sys_mount+0x318/0x380 fs/namespace.c:3606
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3606
 x64_sys_call+0x65d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3414b90eea
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:00007f3415b10e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f3415b10ef0 RCX: 00007f3414b90eea
RDX: 00002000000005c0 RSI: 0000200000000240 RDI: 00007f3415b10eb0
RBP: 00002000000005c0 R08: 00007f3415b10ef0 R09: 0000000003000050
R10: 0000000003000050 R11: 0000000000000246 R12: 0000200000000240
R13: 00007f3415b10eb0 R14: 00000000000014fe R15: 0000200000000600
 </TASK>
================================================================================
exFAT-fs (loop2): unable to set blocksize 33554432
exFAT-fs (loop2): failed to read boot sector
exFAT-fs (loop2): failed to recognize exfat type