linux-kernel - Re: [PATCH] jfs: fix GPF in diFree

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Date:   Wed, 23 Jun 2021 09:13:07 -0500
From:   Dave Kleikamp <dave.kleikamp@...cle.com>
To:     Pavel Skripkin <paskripkin@...il.com>, shaggy@...nel.org
Cc:     jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        syzbot+0a89a7b56db04c21a656@...kaller.appspotmail.com
Subject: Re: [PATCH] jfs: fix GPF in diFree

On 6/6/21 9:24 AM, Pavel Skripkin wrote:
> Avoid passing inode with
> JFS_SBI(inode->i_sb)->ipimap == NULL to
> diFree()[1]. GFP will appear:

I'm a little curious how we get as far as creating and freeing 
non-special inodes if ipimap == NULL.

> 
> 	struct inode *ipimap = JFS_SBI(ip->i_sb)->ipimap;
> 	struct inomap *imap = JFS_IP(ipimap)->i_imap;
> 
> JFS_IP() will return invalid pointer when ipimap == NULL
> 
> Call Trace:
>   diFree+0x13d/0x2dc0 fs/jfs/jfs_imap.c:853 [1]
>   jfs_evict_inode+0x2c9/0x370 fs/jfs/inode.c:154
>   evict+0x2ed/0x750 fs/inode.c:578
>   iput_final fs/inode.c:1654 [inline]
>   iput.part.0+0x3fe/0x820 fs/inode.c:1680
>   iput+0x58/0x70 fs/inode.c:1670

Is there more to the stack trace? Is this part of a failed mount()?

> 
> Reported-and-tested-by: syzbot+0a89a7b56db04c21a656@...kaller.appspotmail.com
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>ipimap == NULL

I don't doubt that this happened, so I'll apply the patch which is 
obviously safe.

> ---
>   fs/jfs/inode.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/jfs/inode.c b/fs/jfs/inode.c
> index 6f65bfa9f18d..b0eb9c85eea0 100644
> --- a/fs/jfs/inode.c
> +++ b/fs/jfs/inode.c
> @@ -151,7 +151,8 @@ void jfs_evict_inode(struct inode *inode)
>   			if (test_cflag(COMMIT_Freewmap, inode))
>   				jfs_free_zero_link(inode);
>   
> -			diFree(inode);
> +			if (JFS_SBI(inode->i_sb)->ipimap)
> +				diFree(inode);
>   
>   			/*
>   			 * Free the inode from the quota allocation.
>