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

[syzbot]

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+dfcbc1...@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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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: [PATCH] Testing the patch...
Author: nsvato...@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master

Signed-off-by: Svyatoslav Nikolenko <nsvato...@gmail.com>
---
fs/f2fs/super.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 6a2f09c61dcd..b6b32bcbc126 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -3934,6 +3934,9 @@ static int __f2fs_commit_super(struct f2fs_sb_info *sbi, struct folio *folio,
blk_opf_t opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH | REQ_FUA;
int ret;

+ if (unlikely(sbi->log_blocksize < 9))
+ return -EFSCORRUPTED;
+
folio_lock(folio);
folio_wait_writeback(folio);
if (update)
--
2.47.3

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+dfcbc1...@syzkaller.appspotmail.com
Tested-by: syzbot+dfcbc1...@syzkaller.appspotmail.com

Tested on:

commit: 3d778354 Add linux-next specific files for 20260923
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=156d9c05580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6993cf63b5648f57

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

patch: https://syzkaller.appspot.com/x/patch.diff?x=11938205580000

Note: testing is done by a robot and is best-effort only.

[Chao Yu]

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

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+dfcbc1...@syzkaller.appspotmail.com
Tested-by: syzbot+dfcbc1...@syzkaller.appspotmail.com

Tested on:

commit: 7d114d27 f2fs: fix to set sbi->log_blocksize in advance
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git bugfix/common
console output: https://syzkaller.appspot.com/x/log.txt?x=17652b15580000
kernel config: https://syzkaller.appspot.com/x/.config?x=40ee55a747aeff44

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

Note: no patches were applied.