linux-kernel - Re: [PATCH v2] i915/perf: Fix NULL deref bugs with drm

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Date:   Fri, 27 Oct 2023 18:38:21 +0100
From:   Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Umesh Nerlige Ramappa <umesh.nerlige.ramappa@...el.com>,
        Matt Roper <matthew.d.roper@...el.com>,
        Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc:     dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com, Tvrtko Ursulin <tvrtko.ursulin@...el.com>
Subject: Re: [PATCH v2] i915/perf: Fix NULL deref bugs with drm_dbg() calls


On 27/10/2023 18:28, Harshit Mogalapalli wrote:
> When i915 perf interface is not available dereferencing it will lead to
> NULL dereferences.
> 
> As returning -ENOTSUPP is pretty clear return when perf interface is not
> available.
> 
> Fixes: 2fec539112e8 ("i915/perf: Replace DRM_DEBUG with driver specific drm_dbg call")
> Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> ---
> v1 --> v2: Remove the debug calls as they don't add much value and
> -ENOTSUPP is a good enough return value.
> ---
>   drivers/gpu/drm/i915/i915_perf.c | 15 +++------------
>   1 file changed, 3 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 2f3ecd7d4804..7b1c8de2f9cb 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -4227,11 +4227,8 @@ int i915_perf_open_ioctl(struct drm_device *dev, void *data,
>   	u32 known_open_flags;
>   	int ret;
>   
> -	if (!perf->i915) {
> -		drm_dbg(&perf->i915->drm,
> -			"i915 perf interface not available for this system\n");
> +	if (!perf->i915)
>   		return -ENOTSUPP;
> -	}
>   
>   	known_open_flags = I915_PERF_FLAG_FD_CLOEXEC |
>   			   I915_PERF_FLAG_FD_NONBLOCK |
> @@ -4607,11 +4604,8 @@ int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
>   	struct i915_oa_reg *regs;
>   	int err, id;
>   
> -	if (!perf->i915) {
> -		drm_dbg(&perf->i915->drm,
> -			"i915 perf interface not available for this system\n");
> +	if (!perf->i915)
>   		return -ENOTSUPP;
> -	}
>   
>   	if (!perf->metrics_kobj) {
>   		drm_dbg(&perf->i915->drm,
> @@ -4773,11 +4767,8 @@ int i915_perf_remove_config_ioctl(struct drm_device *dev, void *data,
>   	struct i915_oa_config *oa_config;
>   	int ret;
>   
> -	if (!perf->i915) {
> -		drm_dbg(&perf->i915->drm,
> -			"i915 perf interface not available for this system\n");
> +	if (!perf->i915)
>   		return -ENOTSUPP;
> -	}
>   
>   	if (i915_perf_stream_paranoid && !perfmon_capable()) {
>   		drm_dbg(&perf->i915->drm,

Thanks for re-spinning it so quickly! LGTM.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>

Regards,

Tvrtko