linux-kernel - Re: [PATCH][next] drm/dp_mst: fix multiple frees of tx->bytes

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Date:   Wed, 20 Nov 2019 13:59:19 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     Colin King <colin.king@...onical.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] drm/dp_mst: fix multiple frees of tx->bytes

Heh, surprised I missed this one!

Reviewed-by: Lyude Paul <lyude@...hat.com>

Do you need me to push this to drm-misc, or do you have commit rights already?

On Wed, 2019-11-20 at 17:35 +0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently tx->bytes is being freed r->num_transactions number of
> times because tx is not being set correctly. Fix this by setting
> tx to &r->transactions[i] so that the correct objects are being
> freed on each loop iteration.
> 
> Addresses-Coverity: ("Double free")
> Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing +
> selftests")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index ae5809a1f19a..2754e7e075e7 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -517,8 +517,10 @@ drm_dp_decode_sideband_req(const struct
> drm_dp_sideband_msg_tx *raw,
>  			}
>  
>  			if (failed) {
> -				for (i = 0; i < r->num_transactions; i++)
> +				for (i = 0; i < r->num_transactions; i++) {
> +					tx = &r->transactions[i];
>  					kfree(tx->bytes);
> +				}
>  				return -ENOMEM;
>  			}
>  
-- 
Cheers,
	Lyude Paul