CVE-2025-68769

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix return value of f2fs_recover_fsync_data()

With below scripts, it will trigger panic in f2fs:

mkfs.f2fs -f /dev/vdd
mount /dev/vdd /mnt/f2fs
touch /mnt/f2fs/foo
sync
echo 111 >> /mnt/f2fs/foo
f2fs_io fsync /mnt/f2fs/foo
f2fs_io shutdown 2 /mnt/f2fs
umount /mnt/f2fs
mount -o ro,norecovery /dev/vdd /mnt/f2fs
or
mount -o ro,disable_roll_forward /dev/vdd /mnt/f2fs

F2FS-fs (vdd): f2fs_recover_fsync_data: recovery fsync data, check_only: 0
F2FS-fs (vdd): Mounted with checkpoint version = 7f5c361f
F2FS-fs (vdd): Stopped filesystem due to reason: 0
F2FS-fs (vdd): f2fs_recover_fsync_data: recovery fsync data, check_only: 1
Filesystem f2fs get_tree() didn't set fc->root, returned 1
------------[ cut here ]------------
kernel BUG at fs/super.c:1761!
Oops: invalid opcode: 0000 [#1] SMP PTI
CPU: 3 UID: 0 PID: 722 Comm: mount Not tainted 6.18.0-rc2+ #721 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:vfs_get_tree.cold+0x18/0x1a
Call Trace:
 <TASK>
 fc_mount+0x13/0xa0
 path_mount+0x34e/0xc50
 __x64_sys_mount+0x121/0x150
 do_syscall_64+0x84/0x800
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fa6cc126cfe

The root cause is we missed to handle error number returned from
f2fs_recover_fsync_data() when mounting image w/ ro,norecovery or
ro,disable_roll_forward mount option, result in returning a positive
error number to vfs_get_tree(), fix it.