Re: [syzbot] [f2fs?] UBSAN: shift-out-of-bounds in __f2fs_commit_super

[Chao Yu <chao@kernel.org>]

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/common

On 9/24/26 13:00, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a8c591ed6b67 Add linux-next specific files for 20260922
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=16f98405580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=19be71c9d7429efd
> dashboard link: https://syzkaller.appspot.com/bug?extid=dfcbc1741488709db4b2
> compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f98405580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=148ea515580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/08a28cd722c6/disk-a8c591ed.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/e1c983b28f94/vmlinux-a8c591ed.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/ff7b15260591/bzImage-a8c591ed.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/3e937ffb1f11/mount_0.gz
>    fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=16029405580000)
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+dfcbc1741488709db4b2@syzkaller.appspotmail.com
> 
> loop0: detected capacity change from 0 to 40427
> ------------[ cut here ]------------
> UBSAN: shift-out-of-bounds in fs/f2fs/super.c:3950:27
> shift exponent 4294967287 is too large for 64-bit type 'sector_t' (aka 'unsigned long long')
> CPU: 1 UID: 0 PID: 5622 Comm: syz-executor329 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
>   ubsan_epilogue+0xa/0x30 lib/ubsan.c:233
>   __ubsan_handle_shift_out_of_bounds+0x36d/0x400 lib/ubsan.c:494
>   __f2fs_commit_super+0x43e/0x4d0 fs/f2fs/super.c:3950
>   sanity_check_area_boundary+0x7c5/0xe20 fs/f2fs/super.c:4040
>   sanity_check_raw_super fs/f2fs/super.c:4215 [inline]
>   read_raw_super_block fs/f2fs/super.c:4625 [inline]
>   f2fs_fill_super+0x1920/0x7fa0 fs/f2fs/super.c:5160
>   get_tree_bdev_flags+0x430/0x4f0 fs/super.c:1872
>   vfs_get_tree+0x92/0x2a0 fs/super.c:1932
>   fc_mount fs/namespace.c:1198 [inline]
>   do_new_mount_fc fs/namespace.c:3772 [inline]
>   do_new_mount+0x319/0xdc0 fs/namespace.c:3848
>   do_mount fs/namespace.c:4181 [inline]
>   __do_sys_mount fs/namespace.c:4394 [inline]
>   __se_sys_mount+0x31d/0x420 fs/namespace.c:4371
>   do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
>   do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f2eb02deeaa
> Code: 56 53 b8 9d 00 00 00 0f 05 83 f8 ea 75 a2 c7 05 e4 5b 09 00 00 00 00 00 eb 96 e8 51 05 00 00 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 d8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffcaf01ba78 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
> RAX: ffffffffffffffda RBX: 00007ffcaf01ba90 RCX: 00007f2eb02deeaa
> RDX: 0000200000000080 RSI: 0000200000000000 RDI: 00007ffcaf01ba90
> RBP: 0000200000000000 R08: 00007ffcaf01bad0 R09: 0000000000000000
> R10: 0000000000200000 R11: 0000000000000286 R12: 0000200000000080
> R13: 00007ffcaf01bad0 R14: 0000000000000003 R15: 0000000000200000
>   </TASK>
> ---[ end trace ]---
> 
> 
> ---
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