linux-kernel - Re: [PATCH] crypto: fix uninit-value in af_alg_free

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Date:   Mon, 14 Aug 2023 09:26:49 +0100
From:   David Howells <dhowells@...hat.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     dhowells@...hat.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, pabeni@...hat.com,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+cba21d50095623218389@...kaller.appspotmail.com
Subject: Re: [PATCH] crypto: fix uninit-value in af_alg_free_resources

Pavel Skripkin <paskripkin@...il.com> wrote:

> Syzbot was able to trigger use of uninitialized memory in
> af_alg_free_resources.
> 
> Bug is caused by missing initialization of rsgl->sgl.need_unpin before
> adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
> is left with uninitialized need_unpin which is read during clean up

Looks feasible :-).

> +		rsgl->sgl.need_unpin = 0;
> +

The blank line isn't really necessary and it's a bool, so can you use 'false'
rather than '0'?

Alternatively, it might be better to move:

		rsgl->sgl.need_unpin =
			iov_iter_extract_will_pin(&msg->msg_iter);

up instead.

David