linux-kernel - Re: [PATCH v2] net: 9p: avoid freeing uninit memory in p9pdu

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Date:   Tue, 5 Dec 2023 18:31:42 +0900
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Fedor Pchelkin <pchelkin@...ras.ru>
Cc:     Latchesar Ionkov <lucho@...kov.net>,
        Eric Van Hensbergen <ericvh@...nel.org>,
        Christian Schoenebeck <linux_oss@...debyte.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, v9fs@...ts.linux.dev,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH v2] net: 9p: avoid freeing uninit memory in p9pdu_vreadf

Fedor Pchelkin wrote on Tue, Dec 05, 2023 at 12:19:50PM +0300:
> If an error occurs while processing an array of strings in p9pdu_vreadf
> then uninitialized members of *wnames array are freed.
> 
> Fix this by iterating over only lower indices of the array. Also handle
> possible uninit *wnames usage if first p9pdu_readf() call inside 'T' case
> fails.
> 
> Found by Linux Verification Center (linuxtesting.org).
> 
> Fixes: ace51c4dd2f9 ("9p: add new protocol support code")
> Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
> ---
> v2: I've missed that *wnames can also be left uninitialized. Please
> ignore the patch v1.

While I agree it's good to initialize it in general, how is that a
problem here? Do we have users that'd ignore the return code and try to
use *wnames?
(The first initialization is required in case the first p9pdu_readf
fails and *wnames had a non-null initial value, but the second is
unrelated)

I don't mind the change even if there isn't but let's add a word in the
commit message.

> As an answer to Dominique's comment: my organization marks this
> statement in all commits.

Fair enough, I think you'd get more internet points with a 'Reported-by'
but I see plenty of such messages in old commits and this isn't
something I want to argue about -- ok.

-- 
Dominique Martinet | Asmadeus