Nouveau - Oct 2024 - [PATCH v3 1/2] nouveau/dmem: Fix privileged error in copy engine channel

From: Yonatan Maman <Ymaman at Nvidia.com>

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

- Vulnerability in migrate_to_ram: The migrate_to_ram function might
  return a dirty HIGH_USER page when a copy push command (FW channel)
  fails, potentially exposing sensitive data and posing a security
  risk. To mitigate this, the patch ensures the allocation of a non-dirty
  (zero) page for the destination, preventing the return of a dirty page
  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 V2:
- Fixed version according to Danilo Krummrich's comments.


Yonatan Maman (2):
  nouveau/dmem: Fix privileged error in copy engine channel
  nouveau/dmem: Fix vulnerability 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>
Co-developed-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>

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 at Nvidia.com>
Signed-off-by: Gal Shalom <GalShalom at Nvidia.com>
Co-developed-by: Gal Shalom <GalShalom at Nvidia.com>
Reviewed-by: Ben Skeggs <bskeggs at nvidia.com>
Cc: stable at vger.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 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