linux-kernel - Re: [Intel-gfx] [PATCH 1/1] drm/i915: fix race condition UAF in i915_perf_add_config

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Date:   Tue, 28 Mar 2023 22:57:32 +0200
From:   Andi Shyti <andi.shyti@...ux.intel.com>
To:     Min Li <lm0963hack@...il.com>
Cc:     jani.nikula@...ux.intel.com, intel-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        daniel@...ll.ch, rodrigo.vivi@...el.com, airlied@...il.com
Subject: Re: [Intel-gfx] [PATCH 1/1] drm/i915: fix race condition UAF in
 i915_perf_add_config_ioctl

Hi Min,

On Tue, Mar 28, 2023 at 05:36:27PM +0800, Min Li wrote:
> Userspace can guess the id value and try to race oa_config object creation
> with config remove, resulting in a use-after-free if we dereference the
> object after unlocking the metrics_lock.  For that reason, unlocking the
> metrics_lock must be done after we are done dereferencing the object.
> 
> Signed-off-by: Min Li <lm0963hack@...il.com>

Thank you for your patch!

Reviewed-by: Andi Shyti <andi.shyti@...ux.intel.com>

Andi

> ---
>  drivers/gpu/drm/i915/i915_perf.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
> index 824a34ec0b83..93748ca2c5da 100644
> --- a/drivers/gpu/drm/i915/i915_perf.c
> +++ b/drivers/gpu/drm/i915/i915_perf.c
> @@ -4634,13 +4634,13 @@ int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
>  		err = oa_config->id;
>  		goto sysfs_err;
>  	}
> -
> -	mutex_unlock(&perf->metrics_lock);
> +	id = oa_config->id;
>  
>  	drm_dbg(&perf->i915->drm,
>  		"Added config %s id=%i\n", oa_config->uuid, oa_config->id);
> +	mutex_unlock(&perf->metrics_lock);
>  
> -	return oa_config->id;
> +	return id;
>  
>  sysfs_err:
>  	mutex_unlock(&perf->metrics_lock);
> -- 
> 2.25.1