Nouveau - Sep 2024 - [PATCH 2/2] nouveau/dmem: Fix memory leak in `migrate_to_ram` upon copy error

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

- 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 the security of the driver 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 addresses this by adjusting the Copy
Engine channel configuration to permit privileged push commands, thus resolving
the error.

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

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: 6de125383a5cc
Signed-off-by: Yonatan Maman <Ymaman at Nvidia.com>
Signed-off-by: Gal Shalom <GalShalom 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

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.

Signed-off-by: Yonatan Maman <Ymaman at Nvidia.com>
Signed-off-by: Gal Shalom <GalShalom 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