Re: [PATCH] drm/nouveau/gsp: fix potential leak of memory used during acpi init

[Danilo Krummrich <dakr@kernel.org>]

On Tue, Jun 17, 2025 at 01:29:20PM +0200, Philipp Stanner wrote:
> On Tue, 2025-06-17 at 14:00 +1000, Ben Skeggs wrote:
> > diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/gsp.c
> > b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/gsp.c
> > index baf42339f93e..b098a7555fde 100644
> > --- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/gsp.c
> > +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/gsp.c
> 
> This seems to be based on a code move that is not yet in mainline.

It is, it did land with v6.16-rc1.

> Therefore, backporting the bugfix to stable seems difficult. Since that
> code move is already in drm-misc-next, it would seem that it can only
> be solved with two distinct patches for stable and for -next.

drm-misc-fixes is the relevant target branch and given the above, it contains
the code move as well.

However, you're right that this fix won't apply to anything before v6.16-rc1.
Given that, it makes sense to leave a note below the '---' line that this fix
won't apply before v6.16-rc1 and that a backported patch will be sent to stable
once this one hit Linus' tree.

> But this needs to be judged by a maintainer.
> 
> > @@ -719,7 +719,6 @@ r535_gsp_acpi_caps(acpi_handle handle,
> > CAPS_METHOD_DATA *caps)
> >  	union acpi_object argv4 = {
> >  		.buffer.type    = ACPI_TYPE_BUFFER,
> >  		.buffer.length  = 4,
> > -		.buffer.pointer = kmalloc(argv4.buffer.length,
> > GFP_KERNEL),
> >  	}, *obj;
> >  
> >  	caps->status = 0xffff;
> > @@ -727,17 +726,22 @@ r535_gsp_acpi_caps(acpi_handle handle,
> > CAPS_METHOD_DATA *caps)
> >  	if (!acpi_check_dsm(handle, &NVOP_DSM_GUID, NVOP_DSM_REV,
> > BIT_ULL(0x1a)))
> >  		return;
> >  
> > +	argv4.buffer.pointer = kmalloc(argv4.buffer.length,
> > GFP_KERNEL);
> > +	if (!argv4.buffer.pointer)
> > +		return;
> > +
> 
> This could be done immediately after the creation of argv4. That way
> it's more difficult to have the leak again if something is inserted
> later on.

I think the idea was to avoid a potential unwind path after acpi_check_dsm().

> >  	obj = acpi_evaluate_dsm(handle, &NVOP_DSM_GUID,
> > NVOP_DSM_REV, 0x1a, &argv4);
> >  	if (!obj)
> > -		return;
> > +		goto done;
> >  
> >  	if (WARN_ON(obj->type != ACPI_TYPE_BUFFER) ||
> >  	    WARN_ON(obj->buffer.length != 4))
> > -		return;
> > +		goto done;
> >  
> >  	caps->status = 0;
> >  	caps->optimusCaps = *(u32 *)obj->buffer.pointer;
> >  
> > +done:
> >  	ACPI_FREE(obj);
> >  
> >  	kfree(argv4.buffer.pointer);
> > @@ -754,24 +758,28 @@ r535_gsp_acpi_jt(acpi_handle handle,
> > JT_METHOD_DATA *jt)
> >  	union acpi_object argv4 = {
> >  		.buffer.type    = ACPI_TYPE_BUFFER,
> >  		.buffer.length  = sizeof(caps),
> > -		.buffer.pointer = kmalloc(argv4.buffer.length,
> > GFP_KERNEL),
> >  	}, *obj;
> >  
> >  	jt->status = 0xffff;
> >  
> > +	argv4.buffer.pointer = kmalloc(argv4.buffer.length,
> > GFP_KERNEL);
> > +	if (!argv4.buffer.pointer)
> > +		return;
> > +
> >  	obj = acpi_evaluate_dsm(handle, &JT_DSM_GUID, JT_DSM_REV,
> > 0x1, &argv4);
> >  	if (!obj)
> > -		return;
> > +		goto done;
> >  
> >  	if (WARN_ON(obj->type != ACPI_TYPE_BUFFER) ||
> >  	    WARN_ON(obj->buffer.length != 4))
> > -		return;
> > +		goto done;
> >  
> >  	jt->status = 0;
> >  	jt->jtCaps = *(u32 *)obj->buffer.pointer;
> >  	jt->jtRevId = (jt->jtCaps & 0xfff00000) >> 20;
> >  	jt->bSBIOSCaps = 0;
> >  
> > +done:
> 
> 'done' seems like a bad name considering that the operations are
> aborted with a WARN_ON above. Better 'abort' or sth like that.

I think some neutral name is fine, since we also enter this code path when
everything went well, maybe 'out_free' or just 'free'?

> P.
> 
> >  	ACPI_FREE(obj);
> >  
> >  	kfree(argv4.buffer.pointer);
>