linux-kernel - Re: [PATCH] [v2] qed: Fix a potential use-after-free in qed_cxt_tables

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Message-ID: <20231208155957.088c372b@kernel.org>
Date:   Fri, 8 Dec 2023 15:59:57 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
Cc:     Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Yuval Mintz <Yuval.Mintz@...gic.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] qed: Fix a potential use-after-free in
 qed_cxt_tables_alloc

On Thu,  7 Dec 2023 17:36:06 +0800 Dinghao Liu wrote:
> v2: -Change the bug type from double-free to use-after-free.
>     -Move the null check against p_mngr->ilt_shadow to the beginning
>      of the function qed_ilt_shadow_free().
>     -When kcalloc() fails in qed_ilt_shadow_alloc(), just return
>      because there is nothing to free.

This refactoring is not acceptable as part of a fix, sorry.

> @@ -933,6 +936,7 @@ static void qed_ilt_shadow_free(struct qed_hwfn *p_hwfn)
>  		p_dma->virt_addr = NULL;
>  	}
>  	kfree(p_mngr->ilt_shadow);
> +	p_hwfn->p_cxt_mngr->ilt_shadow = NULL;

Why do you dereference p_hwfn here?
Seems more natural to use:

	p_mngr->ilt_shadow = NULL;

since that's the exact pointer that was passed to free.
-- 
pw-bot: cr