Nouveau - Oct 2024 - [PATCH v2 1/2] nouveau/dmem: Fix privileged error in copy engine channel

From: Yonatan Maman <Ymaman at Nvidia.com>

Date: Mon, 7 Oct 2024 14:48:26 +0300
Subject: [PATCH v2 0/2] drm/nouveau/dmem: Fix Memory Leaking and Device Channels
configuration

This patch series addresses two critical issues in the Nouveau driver
related to device channels, error handling, and memory leaks.

- Memory Leak in migrate_to_ram: The migrate_to_ram function was
  identified as leaking memory when a copy push command fails. This
  results in the function returning a dirty HIGH_USER page, which can
  expose sensitive information and pose a security risk. To mitigate
  this vulnerability, the patch ensures that a zero page is allocated for
  the destination page, thereby preventing memory leaks and enhancing
  driver security in case of failure.

- Privileged Error in Copy Engine Channel: An error was observed when
  the nouveau_dmem_copy_one function is executed, leading to a Host Copy
  Engine Privileged error on channel 1. The patch resolves this by
  adjusting the Copy Engine channel configuration to permit privileged
  push commands, resolving the error.

Changes since V1:
- Fixed version according to Danilo Krummrich's comments.

Yonatan Maman (2):
  nouveau/dmem: Fix privileged error in copy engine channel
  nouveau/dmem: Fix memory leak in `migrate_to_ram` upon copy error

 drivers/gpu/drm/nouveau/nouveau_dmem.c | 2 +-
 drivers/gpu/drm/nouveau/nouveau_drm.c  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

-- 
2.34.1

From: Yonatan Maman <Ymaman at Nvidia.com>

When `nouveau_dmem_copy_one` is called, the following error occurs:

[272146.675156] nouveau 0000:06:00.0: fifo: PBDMA9: 00000004 [HCE_PRIV]
ch 1 00000300 00003386

This indicates that a copy push command triggered a Host Copy Engine
Privileged error on channel 1 (Copy Engine channel). To address this
issue, modify the Copy Engine channel to allow privileged push commands

Fixes: 6de125383a5c ("drm/nouveau/fifo: expose runlist topology info on all
chipsets")
Signed-off-by: Yonatan Maman <Ymaman at Nvidia.com>
Signed-off-by: Gal Shalom <GalShalom at Nvidia.com>
Reviewed-by: Ben Skeggs <bskeggs at nvidia.com>
---
 drivers/gpu/drm/nouveau/nouveau_drm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c
b/drivers/gpu/drm/nouveau/nouveau_drm.c
index a58c31089613..0a75ce4c5021 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -356,7 +356,7 @@ nouveau_accel_ce_init(struct nouveau_drm *drm)
 		return;
 	}
 
-	ret = nouveau_channel_new(drm, device, false, runm, NvDmaFB, NvDmaTT,
&drm->cechan);
+	ret = nouveau_channel_new(drm, device, true, runm, NvDmaFB, NvDmaTT,
&drm->cechan);
 	if (ret)
 		NV_ERROR(drm, "failed to create ce channel, %d\n", ret);
 }
-- 
2.34.1

From: Yonatan Maman <Ymaman at Nvidia.com>

A copy push command might fail, causing `migrate_to_ram` to return a
dirty HIGH_USER page to the user.

This exposes a security vulnerability in the nouveau driver. To prevent
memory leaks in `migrate_to_ram` upon a copy error, allocate a zero
page for the destination page.

Fixes: 5be73b690875 ("drm/nouveau/dmem: device memory helpers for
SVM")
Signed-off-by: Yonatan Maman <Ymaman at Nvidia.com>
Signed-off-by: Gal Shalom <GalShalom at Nvidia.com>
Reviewed-by: Ben Skeggs <bskeggs at nvidia.com>
---
 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 6fb65b01d778..097bd3af0719 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