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

[Chao Yu]

On 2022/8/31 2:09, Jaegeuk Kim wrote:
> On 08/30, 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.
> >
> > Signed-off-by: Chao Yu <chao.yu@xxxxxxxx>
> > ---
> >   fs/f2fs/compress.c |  2 +-
> >   fs/f2fs/f2fs.h     |  1 +
> >   fs/f2fs/inode.c    | 10 +++++++++-
> >   fs/f2fs/super.c    |  4 ++--
> >   4 files changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > index 730256732a9e..c38b22bb6432 100644
> > --- a/fs/f2fs/compress.c
> > +++ b/fs/f2fs/compress.c
> > @@ -1947,7 +1947,7 @@ int f2fs_init_compress_inode(struct f2fs_sb_info *sbi)
> >   	if (!test_opt(sbi, COMPRESS_CACHE))
> >   		return 0;
> >   
> > -	inode = f2fs_iget(sbi->sb, F2FS_COMPRESS_INO(sbi));
> > +	inode = f2fs_iget_inner(sbi->sb, F2FS_COMPRESS_INO(sbi));
> >   	if (IS_ERR(inode))
> >   		return PTR_ERR(inode);
> >   	sbi->compress_inode = inode;
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 408d8034ed74..35f9e1a6a1bf 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -3467,6 +3467,7 @@ int f2fs_pin_file_control(struct inode *inode, bool inc);
> >   void f2fs_set_inode_flags(struct inode *inode);
> >   bool f2fs_inode_chksum_verify(struct f2fs_sb_info *sbi, struct page *page);
> >   void f2fs_inode_chksum_set(struct f2fs_sb_info *sbi, struct page *page);
> > +struct inode *f2fs_iget_inner(struct super_block *sb, unsigned long ino);
> >   struct inode *f2fs_iget(struct super_block *sb, unsigned long ino);
> >   struct inode *f2fs_iget_retry(struct super_block *sb, unsigned long ino);
> >   int f2fs_try_to_free_nats(struct f2fs_sb_info *sbi, int nr_shrink);
> > diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> > index 6d11c365d7b4..0ab3ae9b2110 100644
> > --- a/fs/f2fs/inode.c
> > +++ b/fs/f2fs/inode.c
> > @@ -480,7 +480,7 @@ static int do_read_inode(struct inode *inode)
> >   	return 0;
> >   }
> >   
> > -struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
> > +struct inode *f2fs_iget_inner(struct super_block *sb, unsigned long ino)
> >   {
> >   	struct f2fs_sb_info *sbi = F2FS_SB(sb);
> >   	struct inode *inode;
> > @@ -568,6 +568,14 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
> >   	return ERR_PTR(ret);
> >   }
> >   
> > +struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
> > +{
> > +	if (f2fs_check_nid_range(F2FS_SB(sb), ino))
> > +		return -EINVAL;
>
> EINVAL or EFSCORRUPTED used in f2fs_check_nid_range?

Oh, I guess returning EFSCORRUPTED will be better.

> Do we have a report on this before?

Not yet, but I guess it is possible in a fuzzed image like below paths, due to
we will not check ino before pass it to f2fs_iget(), and then f2fs_iget() will
find/return a hashed internal inode to caller, which should be avoided.

case #1
recover_dentry()

	de = __f2fs_find_entry(dir, &fname, &page);
	if (de && inode->i_ino == le32_to_cpu(de->ino))
		goto out_put;

	if (de) {
		einode = f2fs_iget_retry(inode->i_sb, le32_to_cpu(de->ino));
		if (IS_ERR(einode)) {
			WARN_ON(1);
			err = PTR_ERR(einode);
			if (err == -ENOENT)
				err = -EEXIST;
			goto out_put;
		}

case #2
static int recover_orphan_inode(struct f2fs_sb_info *sbi, nid_t ino)
{
	struct inode *inode;
	struct node_info ni;
	int err;

	inode = f2fs_iget_retry(sbi->sb, ino);

Thanks,

> > +
> > +	return f2fs_iget_inner(sb, ino);
> > +}
> > +
> >   struct inode *f2fs_iget_retry(struct super_block *sb, unsigned long ino)
> >   {
> >   	struct inode *inode;
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index b8e5fe244596..a5f5e7483791 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -4157,7 +4157,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> >   		goto free_xattr_cache;
> >   
> >   	/* get an inode for meta space */
> > -	sbi->meta_inode = f2fs_iget(sb, F2FS_META_INO(sbi));
> > +	sbi->meta_inode = f2fs_iget_inner(sb, F2FS_META_INO(sbi));
> >   	if (IS_ERR(sbi->meta_inode)) {
> >   		f2fs_err(sbi, "Failed to read F2FS meta data inode");
> >   		err = PTR_ERR(sbi->meta_inode);
> > @@ -4265,7 +4265,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
> >   		goto free_nm;
> >   
> >   	/* get an inode for node space */
> > -	sbi->node_inode = f2fs_iget(sb, F2FS_NODE_INO(sbi));
> > +	sbi->node_inode = f2fs_iget_inner(sb, F2FS_NODE_INO(sbi));
> >   	if (IS_ERR(sbi->node_inode)) {
> >   		f2fs_err(sbi, "Failed to read node inode");
> >   		err = PTR_ERR(sbi->node_inode);
> > --
> > 2.25.1