linux-kernel - [PATCH v4 2/2] nouveau/dmem: Fix vulnerability in migrate_to

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Message-ID: <20241008115943.990286-3-ymaman@nvidia.com>
Date: Tue, 8 Oct 2024 14:59:43 +0300
From: Yonatan Maman <ymaman@...dia.com>
To: <kherbst@...hat.com>, <lyude@...hat.com>, <dakr@...hat.com>,
	<airlied@...il.com>, <daniel@...ll.ch>, <bskeggs@...dia.com>,
	<jglisse@...hat.com>, <dri-devel@...ts.freedesktop.org>,
	<nouveau@...ts.freedesktop.org>
CC: Yonatan Maman <Ymaman@...dia.com>, <linux-kernel@...r.kernel.org>,
	<stable@...r.kernel.org>, Gal Shalom <GalShalom@...dia.com>
Subject: [PATCH v4 2/2] nouveau/dmem: Fix vulnerability in migrate_to_ram upon copy error

From: Yonatan Maman <Ymaman@...dia.com>

The `nouveau_dmem_copy_one` function ensures that the copy push command is
sent to the device firmware but does not track whether it was executed
successfully.

In the case of a copy error (e.g., firmware or hardware failure), the
copy push command will be sent via the firmware channel, and
`nouveau_dmem_copy_one` will likely report success, leading to the
`migrate_to_ram` function returning a dirty HIGH_USER page to the user.

This can result in a security vulnerability, as a HIGH_USER page that may
contain sensitive or corrupted data could be returned to the user.

To prevent this vulnerability, we allocate a zero page. Thus, in case of
an error, a non-dirty (zero) page will be returned to the user.

Fixes: 5be73b690875 ("drm/nouveau/dmem: device memory helpers for SVM")
Signed-off-by: Yonatan Maman <Ymaman@...dia.com>
Co-developed-by: Gal Shalom <GalShalom@...dia.com>
Signed-off-by: Gal Shalom <GalShalom@...dia.com>
Reviewed-by: Ben Skeggs <bskeggs@...dia.com>
Cc: stable@...r.kernel.org
---
 drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 1f2d649f4b96..1a072568cef6 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -193,7 +193,7 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct vm_fault *vmf)
 	if (!spage || !(src & MIGRATE_PFN_MIGRATE))
 		goto done;

-	dpage = alloc_page_vma(GFP_HIGHUSER, vmf->vma, vmf->address);
+	dpage = alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO, vmf->vma, vmf->address);
 	if (!dpage)
 		goto done;

-- 
2.34.1