linux-kernel - Re: [PATCH] md: fix an incorrect NULL check in md_reload

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Date:   Fri,  8 Apr 2022 16:47:40 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     song@...nel.org
Cc:     guoqing.jiang@...ux.dev, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, rgoldwyn@...e.com,
        stable@...r.kernel.org, xiam0nd.tong@...il.com
Subject: Re: [PATCH] md: fix an incorrect NULL check in md_reload_sb

On Thu, 7 Apr 2022 17:37:55 -0700, Song Liu wrote:
> On Mon, Mar 28, 2022 at 1:06 AM Xiaomeng Tong <xiam0nd.tong@...il.com> wrote:
> >
> > The bug is here:
> >         if (!rdev || rdev->desc_nr != nr) {
> >
> > The list iterator value 'rdev' will *always* be set and non-NULL
> > by rdev_for_each_rcu(), so it is incorrect to assume that the
> > iterator value will be NULL if the list is empty or no element
> > found (In fact, it will be a bogus pointer to an invalid struct
> > object containing the HEAD). Otherwise it will bypass the check
> > and lead to invalid memory access passing the check.
> >
> > To fix the bug, use a new variable 'iter' as the list iterator,
> > while using the original variable 'pdev' as a dedicated pointer to
> > point to the found element.
> >
> > Cc: stable@...r.kernel.org
> > Fixes: 70bcecdb1534 ("amd-cluster: Improve md_reload_sb to be less error prone")
> 
> s/amd-cluster/md-cluster/

Have fixed it in PATCH v3, please check it. Thank you.

--
Xiaomeng Tong