Re: [PATCH v2] f2fs: fix to disallow getting inner inode via f2fs_iget()

From: Chao Yu
Date: Thu Sep 08 2022 - 00:04:35 EST


On 2022/9/8 10:19, Jaegeuk Kim wrote:
On 09/08, Chao Yu wrote:
On 2022/9/8 10:02, Jaegeuk Kim wrote:
On 08/31, Chao Yu wrote:
From: Chao Yu <chao.yu@xxxxxxxx>

Introduce f2fs_iget_inner() for f2fs_fill_super() to get inner inode:
meta inode, node inode or compressed inode, and add f2fs_check_nid_range()
in f2fs_iget() to avoid getting inner inode from external interfaces.

So, we don't want to check the range of inner inode numbers? What'd be the
way to check it's okay?

For node_ino, meta_ino, root_ino, we have checked them in sanity_check_raw_super()
as below:

/* check reserved ino info */
if (le32_to_cpu(raw_super->node_ino) != 1 ||
le32_to_cpu(raw_super->meta_ino) != 2 ||
le32_to_cpu(raw_super->root_ino) != 3) {
f2fs_info(sbi, "Invalid Fs Meta Ino: node(%u) meta(%u) root(%u)",
le32_to_cpu(raw_super->node_ino),
le32_to_cpu(raw_super->meta_ino),
le32_to_cpu(raw_super->root_ino));
return -EFSCORRUPTED;
}

compressed_ino should always be NM_I(sbi)->max_nid, it can be checked in
f2fs_init_compress_inode()?

Hmm, I'm not sure whether we really need this patch, since it'd look better
to handle all the iget with single f2fs_iget?

Well, the main concern is previously f2fs_iget() won't check validation for inner
inode due to it will skip do_read_inode() - f2fs_check_nid_range(), so that in a
fuzzed image, caller may pass inner ino into f2fs_iget(), result in incorrect use
of inner inode. So I add f2fs_check_nid_range() in prior to f2fs_iget_inner() in
f2fs_iget() as below to detect and avoid this case.

+struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
+{
+ int ret;
+
+ ret = f2fs_check_nid_range(F2FS_SB(sb), ino);
+ if (ret)
+ return ERR_PTR(ret);
+
+ return f2fs_iget_inner(sb, ino);