linux-kernel - Re: [PATCH] f2fs: fix to disallow getting inner inode via f2fs

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Message-ID: <b1c74dc1-8d01-9041-9469-036273c5618d@kernel.org>
Date:   Wed, 31 Aug 2022 06:44:45 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <chao.yu@...o.com>
Subject: Re: [PATCH] f2fs: fix to disallow getting inner inode via f2fs_iget()

On 2022/8/31 2:09, Jaegeuk Kim wrote:
> On 08/30, Chao Yu wrote:
>> From: Chao Yu <chao.yu@...o.com>
>>
>> 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@...o.com>
>> ---
>>   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