[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <33f459af-7731-fb39-ec6f-059cf1a77bb4@amd.com>
Date: Thu, 20 Jan 2022 13:04:02 -0500
From: Felix Kuehling <felix.kuehling@....com>
To: Miaoqian Lin <linmq006@...il.com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
"Pan, Xinhui" <Xinhui.Pan@....com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Hawking Zhang <Hawking.Zhang@....com>,
John Clements <john.clements@....com>,
Jonathan Kim <jonathan.kim@....com>,
Bernard Zhao <bernard@...o.com>,
Kevin Wang <kevin1.wang@....com>,
shaoyunl <shaoyun.liu@....com>,
Tian Tao <tiantao6@...ilicon.com>,
amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amdgpu: Fix double free in amdgpu_get_xgmi_hive
Am 2022-01-20 um 5:17 a.m. schrieb Miaoqian Lin:
> Callback function amdgpu_xgmi_hive_release() in kobject_put()
> calls kfree(hive), So we don't need call kfree(hive) again.
>
> Fixes: 7b833d680481 ("drm/amd/amdgpu: fix potential memleak")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
The patch is
Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>
This kobject_init_and_add error handling semantics is very unintuitive,
and we keep stumbling over it. I wonder is there is a better way to
handle this. Basically, this is what it looks like, when done correctly:
foo = kzalloc(sizeof(*foo), GFP_KERNEL);
if (!foo)
return -ENOMEM;
r = kobject_init_and_add(&foo->kobj, &foo_type, &parent, "foo_name");
if (r) {
/* OK, initialization failed, but I still need to
* clean up manually as if the call had succeeded.
*/
kobject_put(&foo->kobj);
/* Don't kfree foo, because that's already done by
* a callback setup by the call that failed above.
*/
return r;
}
Given that unintuitive behaviour, I'd argue that kobject_init_and_add
fails as an abstraction. Code would be clearer, more intuitive and safer
by calling kobject_init and kobject_add separately itself.
kobject_init_and_add saves you typing exactly one line of code, and it's
just not worth it:
foo = kzalloc(sizeof(*foo), GFP_KERNEL);
if (!foo)
return -ENOMEM;
kobject_init(&foo->kobj, &foo_type); /* never fails */
r = kobject_add(&foo->kobj, &parent, "foo_name");
if (r) {
/* since kobj_init succeeded, it's obvious that kobj_put
* is the right thing to do to handle all the cleanup.
*/
kobject_put(&foo->kobj);
return r;
}
Regards,
Felix
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
> index e8b8f28c2f72..35d4b966ef2c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
> @@ -393,7 +393,6 @@ struct amdgpu_hive_info *amdgpu_get_xgmi_hive(struct amdgpu_device *adev)
> if (ret) {
> dev_err(adev->dev, "XGMI: failed initializing kobject for xgmi hive\n");
> kobject_put(&hive->kobj);
> - kfree(hive);
> hive = NULL;
> goto pro_end;
> }
Powered by blists - more mailing lists