linux-kernel - Re: [PATCH 3.16 52/63] xfs: validate cached inodes are free when allocated

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Message-ID: <20180922052659.GC19103@rh>
Date:   Sat, 22 Sep 2018 15:26:59 +1000
From:   Dave Chinner <dchinner@...hat.com>
To:     Ben Hutchings <ben@...adent.org.uk>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        akpm@...ux-foundation.org, Christoph Hellwig <hch@....de>,
        Wen Xu <wen.xu@...ech.edu>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: Re: [PATCH 3.16 52/63] xfs: validate cached inodes are free when
 allocated

On Sat, Sep 22, 2018 at 01:15:42AM +0100, Ben Hutchings wrote:
> 3.16.58-rc1 review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dave Chinner <dchinner@...hat.com>
> 
> commit afca6c5b2595fc44383919fba740c194b0b76aff upstream.
> 
> A recent fuzzed filesystem image cached random dcache corruption
> when the reproducer was run. This often showed up as panics in
> lookup_slow() on a null inode->i_ops pointer when doing pathwalks.
.....
> [bwh: Backported to 3.16:
>  - Look up mode in XFS inode, not VFS inode
>  - Use positive error codes, and EIO instead of EFSCORRUPTED]

Again, why EIO?

And ....
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> ---
>  fs/xfs/xfs_icache.c | 73 +++++++++++++++++++++++++++++----------------
>  1 file changed, 48 insertions(+), 25 deletions(-)
> 
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -133,6 +133,46 @@ xfs_inode_free(
>  }
>  
>  /*
> + * If we are allocating a new inode, then check what was returned is
> + * actually a free, empty inode. If we are not allocating an inode,
> + * then check we didn't find a free inode.
> + *
> + * Returns:
> + *	0		if the inode free state matches the lookup context
> + *	ENOENT		if the inode is free and we are not allocating
> + *	EFSCORRUPTED	if there is any state mismatch at all

You changed the code but not the comment.

Cheers,

Dave.
-- 
Dave Chinner
dchinner@...hat.com