linux-kernel - Re: [PATCH v4] f2fs: add check for deleted inode

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Message-ID: <Z6zQoyNp5td-Wgd1@google.com>
Date: Wed, 12 Feb 2025 16:47:31 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao@...nel.org>
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Leo Stone <leocstone@...il.com>,
	syzbot+b01a36acd7007e273a83@...kaller.appspotmail.com
Subject: Re: [PATCH v4] f2fs: add check for deleted inode

On 02/12, Chao Yu wrote:
> From: Leo Stone <leocstone@...il.com>
> 
> The syzbot reproducer mounts a f2fs image, then tries to unlink an
> existing file. However, the unlinked file already has a link count of 0
> when it is read for the first time in do_read_inode().
> 
> Add a check to sanity_check_inode() for i_nlink == 0.
> 
> [Chao Yu: rebase the code and fix orphan inode recovery issue]
> Reported-by: syzbot+b01a36acd7007e273a83@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=b01a36acd7007e273a83
> Fixes: 39a53e0ce0df ("f2fs: add superblock and major in-memory structure")
> Signed-off-by: Leo Stone <leocstone@...il.com>
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>  fs/f2fs/checkpoint.c | 4 ++++
>  fs/f2fs/f2fs.h       | 1 +
>  fs/f2fs/inode.c      | 6 ++++++
>  3 files changed, 11 insertions(+)
> 
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index bd890738b94d..ada2c548645c 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -751,6 +751,8 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>  	if (is_sbi_flag_set(sbi, SBI_IS_WRITABLE))
>  		f2fs_info(sbi, "orphan cleanup on readonly fs");
>  
> +	set_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);

What about using SBI_POR_DOING?

> +
>  	start_blk = __start_cp_addr(sbi) + 1 + __cp_payload(sbi);
>  	orphan_blocks = __start_sum_addr(sbi) - 1 - __cp_payload(sbi);
>  
> @@ -778,9 +780,11 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>  		}
>  		f2fs_put_page(page, 1);
>  	}
> +
>  	/* clear Orphan Flag */
>  	clear_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG);
>  out:
> +	clear_sbi_flag(sbi, SBI_ORPHAN_RECOVERY);
>  	set_sbi_flag(sbi, SBI_IS_RECOVERED);
>  
>  	return err;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 05879c6dc4d6..1c75081c0c14 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1322,6 +1322,7 @@ enum {
>  	SBI_IS_CLOSE,				/* specify unmounting */
>  	SBI_NEED_FSCK,				/* need fsck.f2fs to fix */
>  	SBI_POR_DOING,				/* recovery is doing or not */
> +	SBI_ORPHAN_RECOVERY,			/* orphan inodes recovery is doing */
>  	SBI_NEED_SB_WRITE,			/* need to recover superblock */
>  	SBI_NEED_CP,				/* need to checkpoint */
>  	SBI_IS_SHUTDOWN,			/* shutdown by ioctl */
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index d6ad7810df69..02f1b69d03d8 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -386,6 +386,12 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>  		}
>  	}
>  
> +	if (inode->i_nlink == 0 && !is_sbi_flag_set(sbi, SBI_ORPHAN_RECOVERY)) {
> +		f2fs_warn(sbi, "%s: inode (ino=%lx) has a link count of 0",
> +			  __func__, inode->i_ino);
> +		return false;
> +	}
> +
>  	return true;
>  }
>  
> -- 
> 2.48.1.502.g6dc24dfdaf-goog