linux-kernel - Re: [PATCH][next] drm/amdgpu: fix return of an uninitialized value in variable ret

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Date:   Fri, 10 May 2019 14:16:23 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Zhou <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] drm/amdgpu: fix return of an uninitialized value
 in variable ret

On Fri, May 10, 2019 at 11:08:42AM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> In the case where is_enable is false and lo_base_addr is non-zero the
> variable ret has not been initialized and is being checked for non-zero
> and potentially garbage is being returned. Fix this by not returning
> ret but instead returning -EINVAL on the zero lo_base_addr case.
> 
> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: a6ac0b44bab9 ("drm/amdgpu: add df perfmon regs and funcs for xgmi")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/df_v3_6.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/df_v3_6.c b/drivers/gpu/drm/amd/amdgpu/df_v3_6.c
> index a5c3558869fb..8c09bf994acd 100644
> --- a/drivers/gpu/drm/amd/amdgpu/df_v3_6.c
> +++ b/drivers/gpu/drm/amd/amdgpu/df_v3_6.c
> @@ -398,10 +398,7 @@ static int df_v3_6_start_xgmi_link_cntr(struct amdgpu_device *adev,
>  				NULL);
>  
>  		if (lo_base_addr == 0)
> -			ret = -EINVAL;
> -
> -		if (ret)
> -			return ret;
> +			return -EINVAL;

>From a naive reading of the code without knowing the hardware spec then
you would probably think that lo_base_addr can also be uninitialized.

<sad face emoji>

regards,
dan carpenter