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

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Date:   Mon, 24 Jan 2022 14:19:57 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Zhou Qingyang <zhou1615@....edu>
Cc:     Leo Li <sunpeng.li@....com>, Kangjie Lu <kjlu@....edu>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Lee Jones <lee.jones@...aro.org>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH] drm/amd/display/dc/calcs/dce_calcs: Fix a memleak in calculate_bandwidth()

Applied.  Thanks!

Alex

On Mon, Jan 24, 2022 at 12:05 PM Zhou Qingyang <zhou1615@....edu> 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
>