linux-kernel - Re: [PATCH] drm/amd/display/dc/calcs/dce_calcs: Fix a memleak in calculate

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Date:   Fri, 28 Jan 2022 11:17:41 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zhou Qingyang <zhou1615@....edu>
Cc:     kjlu@....edu, Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Lee Jones <lee.jones@...aro.org>,
        Mario Kleiner <mario.kleiner.de@...il.com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display/dc/calcs/dce_calcs: Fix a memleak in
 calculate_bandwidth()

On Tue, Jan 25, 2022 at 12:55:51AM +0800, Zhou Qingyang wrote:
> In calculate_bandwidth(), the tag free_sclk and free_yclk are reversed,
> which could lead to a memory leak of yclk.
> 
> Fix this bug by changing the location of free_sclk and free_yclk.
> 
> This bug was found by a static analyzer.
> 
> Builds with 'make allyesconfig' show no new warnings,
> and our static analyzer no longer warns about this code.
> 
> Fixes: 2be8989d0fc2 ("drm/amd/display/dc/calcs/dce_calcs: Move some large variables from the stack to the heap")
> Signed-off-by: Zhou Qingyang <zhou1615@....edu>
> ---
> The analysis employs differential checking to identify inconsistent 
> security operations (e.g., checks or kfrees) between two code paths 
> and confirms that the inconsistent operations are not recovered in the
> current function or the callers, so they constitute bugs. 
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
>  drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> index ff5bb152ef49..e6ef36de0825 100644
> --- a/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> +++ b/drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c
> @@ -2033,10 +2033,10 @@ static void calculate_bandwidth(
>  	kfree(surface_type);
>  free_tiling_mode:
>  	kfree(tiling_mode);
> -free_yclk:
> -	kfree(yclk);
>  free_sclk:
>  	kfree(sclk);
> +free_yclk:
> +	kfree(yclk);
>  }
>  
>  /*******************************************************************************
> -- 
> 2.25.1
> 

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