linux-kernel - Re: [PATCH] ocfs2: fix uninitialized variable in ocfs2_dio_wr_get

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Message-ID: <92d4d393-9734-9f7e-4440-20429bdac14f@linux.alibaba.com>
Date:   Wed, 1 Dec 2021 10:24:58 +0800
From:   Joseph Qi <joseph.qi@...ux.alibaba.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Wengang Wang <wen.gang.wang@...cle.com>, ryan.ding@...cle.com,
        Junxiao Bi <junxiao.bi@...cle.com>
Cc:     Joel Becker <jlbec@...lplan.org>,
        Sunil Mushran <sunil.mushran@...cle.com>,
        ocfs2-devel@....oracle.com, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, Mark Fasheh <mark@...heh.com>
Subject: Re: [PATCH] ocfs2: fix uninitialized variable in
 ocfs2_dio_wr_get_block()



On 11/30/21 6:40 PM, Dan Carpenter wrote:
> The callers assume that "*fsdata" is set on the success path, but
> that's not necessarily true on this path.
> 

In ocfs2_page_mkwrite(), since in this case no target page locked, it
will finally return VM_FAULT_NOPAGE (better VM_FAULT_RETRY?) and throw 
to handle_mm_fault(). So no problem as comments described.

But things seems changed since append direct io path started to use
write_[begin/end]. In this path, the target page is expected as NULL.
This needs more discussion.

Thanks,
Joseph

> Fixes: 5cffff9e2986 ("ocfs2: Fix ocfs2_page_mkwrite()")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
> Please review this one EXTRA CAREFULLY.  It's from static analysis and
> the truth is I'm not 100% sure it's correct.  I'm also not sure that
> it's a complete fix.
> 
> Especially, please review how this is called from ocfs2_write_begin()
> to make sure that this doesn't break anything.
> 
> 
>  fs/ocfs2/aops.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index 68d11c295dd3..a74a370f16f0 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -1813,6 +1813,7 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
>  	if (ret == -EAGAIN) {
>  		BUG_ON(wc->w_target_page);
>  		ret = 0;
> +		*fsdata = wc;
>  		goto out_quota;
>  	}
>  
>