linux-kernel - Re: [PATCH v2] drm/xe/hw_engine_group: Fix bad free in xe_hw_engine_setup

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Message-ID: <ZzeNM5dmKb22VoRw@lstrano-desk.jf.intel.com>
Date: Fri, 15 Nov 2024 10:04:35 -0800
From: Matthew Brost <matthew.brost@...el.com>
To: Su Hui <suhui@...china.com>
CC: <balasubramani.vivekanandan@...el.com>, <lucas.demarchi@...el.com>,
	<thomas.hellstrom@...ux.intel.com>, <rodrigo.vivi@...el.com>,
	<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
	<tzimmermann@...e.de>, <airlied@...il.com>, <simona@...ll.ch>,
	<nathan@...nel.org>, <ndesaulniers@...gle.com>, <morbo@...gle.com>,
	<justinstitt@...gle.com>, <francois.dugast@...el.com>,
	<intel-xe@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>, <llvm@...ts.linux.dev>,
	<kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH v2] drm/xe/hw_engine_group: Fix bad free in
 xe_hw_engine_setup_groups()

On Fri, Nov 15, 2024 at 10:49:42AM +0800, Su Hui wrote:
> Clang static checker(scan-build) warning：
> drivers/gpu/drm/xe/xe_hw_engine_group.c: line 134, column 2
> Argument to kfree() is a constant address (18446744073709551604), which
> is not memory allocated by malloc().
> 
> kfree() can only handle NULL pointers instead of negitave error codes.
> When hw_engine_group_alloc() failed, there is a bad kfree call for
> negitave error codes in xe_hw_engine_setup_groups().
> 
> Free 'group' when alloc_workqueue() failed in hw_engine_group_alloc(), and
> remove wrong kfree() in xe_hw_engine_setup_groups() to fix this problem.
> It's safe to remove these kfree() because drmm_add_action_or_reset()
> can free these by calling hw_engine_group_free().
> 
> Fixes: d16ef1a18e39 ("drm/xe/exec: Switch hw engine group execution mode upon job submission")
> Fixes: f784750c670f ("drm/xe/hw_engine_group: Introduce xe_hw_engine_group")
> Signed-off-by: Su Hui <suhui@...china.com>

Thanks for thr fix. Look correct to me.
Reviewed-by: Matthew Brost <matthew.brost@...el.com>

> ---
> v2:
>  - remove wrong destroy_workqueue() and kfree() in v1 patch
> v1:
>  - https://lore.kernel.org/all/20241114063942.3448607-1-suhui@nfschina.com/
> 
>  drivers/gpu/drm/xe/xe_hw_engine_group.c | 32 +++++++------------------
>  1 file changed, 9 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_hw_engine_group.c b/drivers/gpu/drm/xe/xe_hw_engine_group.c
> index 82750520a90a..3bfa002734ad 100644
> --- a/drivers/gpu/drm/xe/xe_hw_engine_group.c
> +++ b/drivers/gpu/drm/xe/xe_hw_engine_group.c
> @@ -58,8 +58,10 @@ hw_engine_group_alloc(struct xe_device *xe)
>  		return ERR_PTR(-ENOMEM);
>  
>  	group->resume_wq = alloc_workqueue("xe-resume-lr-jobs-wq", 0, 0);
> -	if (!group->resume_wq)
> +	if (!group->resume_wq) {
> +		kfree(group);
>  		return ERR_PTR(-ENOMEM);
> +	}
>  
>  	init_rwsem(&group->mode_sem);
>  	INIT_WORK(&group->resume_work, hw_engine_group_resume_lr_jobs_func);
> @@ -84,25 +86,18 @@ int xe_hw_engine_setup_groups(struct xe_gt *gt)
>  	enum xe_hw_engine_id id;
>  	struct xe_hw_engine_group *group_rcs_ccs, *group_bcs, *group_vcs_vecs;
>  	struct xe_device *xe = gt_to_xe(gt);
> -	int err;
>  
>  	group_rcs_ccs = hw_engine_group_alloc(xe);
> -	if (IS_ERR(group_rcs_ccs)) {
> -		err = PTR_ERR(group_rcs_ccs);
> -		goto err_group_rcs_ccs;
> -	}
> +	if (IS_ERR(group_rcs_ccs))
> +		return PTR_ERR(group_rcs_ccs);
>  
>  	group_bcs = hw_engine_group_alloc(xe);
> -	if (IS_ERR(group_bcs)) {
> -		err = PTR_ERR(group_bcs);
> -		goto err_group_bcs;
> -	}
> +	if (IS_ERR(group_bcs))
> +		return PTR_ERR(group_bcs);
>  
>  	group_vcs_vecs = hw_engine_group_alloc(xe);
> -	if (IS_ERR(group_vcs_vecs)) {
> -		err = PTR_ERR(group_vcs_vecs);
> -		goto err_group_vcs_vecs;
> -	}
> +	if (IS_ERR(group_vcs_vecs))
> +		return PTR_ERR(group_vcs_vecs);
>  
>  	for_each_hw_engine(hwe, gt, id) {
>  		switch (hwe->class) {
> @@ -125,15 +120,6 @@ int xe_hw_engine_setup_groups(struct xe_gt *gt)
>  	}
>  
>  	return 0;
> -
> -err_group_vcs_vecs:
> -	kfree(group_vcs_vecs);
> -err_group_bcs:
> -	kfree(group_bcs);
> -err_group_rcs_ccs:
> -	kfree(group_rcs_ccs);
> -
> -	return err;
>  }
>  
>  /**
> -- 
> 2.30.2
>