linux-kernel - Re: [PATCH] md: md2: fix an incorrect NULL check on list iterator

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Message-Id: <20220328075628.25545-1-xiam0nd.tong@gmail.com>
Date:   Mon, 28 Mar 2022 15:56:28 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     guoqing.jiang@...ux.dev
Cc:     linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
        rgoldwyn@...e.com, song@...nel.org, stable@...r.kernel.org,
        xiam0nd.tong@...il.com
Subject: Re: [PATCH] md: md2: fix an incorrect NULL check on list iterator

> I'd suggest to rephrase the subject to "md: fix an incorrect NULL check 
> in md_reload_sb".

Thank you for the suggestion, i will take it in PATCH v2.

> > -	if (!rdev || rdev->desc_nr != nr) {
> > +	if (!rdev) {
> >   		pr_warn("%s: %d Could not find rdev with nr %d\n", __func__, __LINE__, nr);
> >   		return;
> >   	}
> 
> I guess we only need to check desc_nr since rdev should always be valid 
> , and IMO the fix tag
> is not necessary.

No. At least from the pr_warn log, the list can be empty or no element found in it.
If this cases happen, the 'rdev' will be an invalid pointer that point to a invalid
struct containning the HEAD '&((mddev)->disks)'. So this fix is necessary.

--
Xiaomeng Tong