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

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Message-ID: <icjuhtz35zvp5j6zvgbubydbmirbsr4ceasgxr3rk333bj55dp@mp5yf532hd4i>
Date: Mon, 25 Nov 2024 09:56:11 -0800
From: Leo Stone <leocstone@...il.com>
To: Chao Yu <chao@...nel.org>, jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: Add check for deleted inode

On Mon, Nov 25, 2024 at 07:16:41PM +0800, Chao Yu wrote:
> 
> I'm fine w/ this change, but I didn't get it, how did above commit introduce
> this bug?

Hello Chao,

The commit from the bisect didn't exactly introduce this bug, since it
would still be possible to make a different image that does the exact
same thing in the older code.

This commit was blamed in the bisect because it changes the layout of
struct f2fs_inode:

> @@ -271,6 +272,10 @@ struct f2fs_inode {
> 			__le32 i_inode_checksum;/* inode meta checksum */
> 			__le64 i_crtime;	/* creation time */
> 			__le32 i_crtime_nsec;	/* creation time in nano scale */
>+			__le64 i_compr_blocks;	/* # of compressed blocks */
>+			__u8 i_compress_algorithm;	/* compress algorithm */
>+			__u8 i_log_cluster_size;	/* log of cluster size */
>+			__le16 i_padding;		/* padding */
> 			__le32 i_extra_end[0];	/* for attribute size calculation */
> 		} __packed;
> 		__le32 i_addr[DEF_ADDRS_PER_INODE];	/* Pointers to data blocks */

This changes F2FS_TOTAL_EXTRA_ATTR_SIZE, which allows the syzbot
reproducer's inode to pass the sanity check for corrupted i_extra_size.
Before this change, the inode gets rejected as corrupt:

>[   62.794566][ T9662] F2FS-fs (loop0): sanity_check_inode: inode (ino=7) has corrupted i_extra_isize: 36, max: 24

Thanks,
Leo