Re: [PATCH] hfs: return -EIO instead of BUG() in hfs_write_inode()

[Darrick J. Wong]

On Sat, Jun 06, 2026 at 03:58:31PM +0000, David Maximiliano Hermitte wrote:
> hfs: return -EIO instead of BUG() in hfs_write_inode()
> 
> A corrupted or otherwise malformed HFS filesystem image can reach the
> default case in hfs_write_inode(). The current code calls BUG() there,
> which turns an on-disk filesystem condition into a kernel crash.
> 
> Return -EIO instead. The function already has an error-return path at
> that location, so this preserves the existing failure semantics while
> avoiding a reachable kernel BUG.
> 
> The issue is reproducible with the public syzbot C reproducer linked
> below. Before this change, the reproducer triggers a kernel BUG at
> fs/hfs/inode.c with RIP in hfs_write_inode(). After this change, the
> same reproducer no longer triggers kernel BUG, hfs_write_inode, KASAN,
> Oops, Call Trace, or RIP evidence in the validation window.
> 
> Reported-by: syzbot+97e301b4b82ae803d21b@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=97e301b4b82ae803d21b
> Tested-by: David Maximiliano Hermitte <davemadmaxxx@xxxxxxxxx>
> Signed-off-by: David Maximiliano Hermitte <davemadmaxxx@xxxxxxxxx>
> ---
>  fs/hfs/inode.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
> index 89b33a9d46d5..4192f660b64f 100644
> --- a/fs/hfs/inode.c
> +++ b/fs/hfs/inode.c
> @@ -471,7 +471,6 @@ int hfs_write_inode(struct inode *inode, struct writeback_control *wbc)
>  			hfs_btree_write(HFS_SB(inode->i_sb)->cat_tree);
>  			return 0;
>  		default:
> -			BUG();
>  			return -EIO;

If it's a metadata corruption, shouldn't you return EFSCORRUPTED like
the other major filesystems?

--D

>  		}
>  	}
>