[PATCH v5 0/2] Add vm_bind param check to ensure no overlap with kbo AS carveout

[PATCH v5 0/2] Add vm_bind param check to ensure no overlap with kbo AS carveout

[Adrián Larumbe]

Just a quick check to make sure user-supplied vm_bind regions aren't
clashing with the region reserved for kernel bo's.

I tried to introduce a similar check for panthor_vm_alloc_va(), to throw
back an error when mappings of kernel bo's against specific addresses fall
within the auto_va region. However that is not possible, since there's one
FW region that must be mapped right at CSF_MCU_SHARED_REGION_START. That
is usually not a problem, since drm_mm_insert_node_in_range() will pick
the next one available.

v3 also comes with an early bind range overflow check for sparse mappings.

Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
Changes in v5:
- Coalesced uint64 and kbo ranges overflow checks into a single patch.
- Link to v4: https://patch.msgid.link/20260704-vm_bind_checks-v4-0-4705b6ca9f8a@collabora.com

Changes in v4:
- Deleted commit that passes single operation to panthor_vm_prepare_unmap_op_ctx.
- Moved overflow check one step above in the call stack.
- Rearranged the commits in the series.
- Link to v3: https://patch.msgid.link/20260629-vm_bind_checks-v3-0-85e6740f6c2e@collabora.com

Changes in v3:
- Fixed off-by-one error for user va range calculations.
- Added new commit for panthor_vm_prepare_unmap_op_ctx to take a whole operation.
- Added commit with bind range early overflow check.
- Link to v2: https://patch.msgid.link/20260619-vm_bind_checks-v2-0-b51abab35f71@collabora.com

Changes in v2:
- Simplified user VA range with kernel BO range overlap to a single statement.
- Link to v1: https://patch.msgid.link/20260616-vm_bind_checks-v1-0-956198602ae3@collabora.com

To: Boris Brezillon <boris.brezillon@collabora.com>
To: Steven Price <steven.price@arm.com>
To: Liviu Dudau <liviu.dudau@arm.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
To: Maxime Ripard <mripard@kernel.org>
To: Thomas Zimmermann <tzimmermann@suse.de>
To: David Airlie <airlied@gmail.com>
To: Simona Vetter <simona@ffwll.ch>
To: Heiko Stuebner <heiko@sntech.de>
To: Grant Likely <grant.likely@linaro.org>
To: Adrián Larumbe <adrian.larumbe@collabora.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org

---
Adrián Larumbe (2):
      drm/panthor: Add vm_bind region with kbo range overlap check
      drm/panthor: Fix comment to reflect actual struct field name

 drivers/gpu/drm/panthor/panthor_mmu.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
---
base-commit: 8fca3d8dbebf8d960dad7b10db3cb4a61139454b
change-id: 20260614-vm_bind_checks-46075ba069a0

Best regards,
--  
Adrián Larumbe <adrian.larumbe@collabora.com>

[PATCH v5 1/2] drm/panthor: Add vm_bind region with kbo range overlap check

[Adrián Larumbe]

When a VM is created, caller has to specify the range of the address space
carve-out set aside for mapping kernel BO's. That means vm_bind mappings of
UM-exposed BO's should not intersect with that region, but at the moment
we're not checking this.

At first, I thought of giving these values to drm_gpuvm_init() through its
reserve_{offset, range} arguments, but it turns out that is meant for VM
address spans that are not managed through the usual drm_gpuvm split/merge
circuit, so storing the end of the user VA range at VM creation time and
doing a quick check in the vm_bind ioctl path was the simplest workaround.

The new check also makes sure vm_bind range doesn't overflow the size of a
64-bit unsigned integer. That was already being done further down the call
stack inside drm_gpuvm_sm_map -> drm_gpuvm_range_valid, but it's best to
fail early in the driver before GPUVM functions are invoked so that we
won't waste time allocating vm_bind context resources.

Fixes: tag and reference the relevant sparse binding support commit.
Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 31cc57029c12..910c8e579770 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -310,6 +310,9 @@ struct panthor_vm {
 		u64 end;
 	} kernel_auto_va;
 
+	/** @user_va_range: Upper boundary of VAs VM users can map objects against. */
+	u64 user_va_range;
+
 	/** @as: Address space related fields. */
 	struct {
 		/**
@@ -2893,6 +2896,8 @@ panthor_vm_create(struct panthor_device *ptdev, bool for_mcu,
 		va_range = full_va_range;
 	}
 
+	vm->user_va_range = kernel_va_start;
+
 	mutex_init(&vm->mm_lock);
 	drm_mm_init(&vm->mm, kernel_va_start, kernel_va_size);
 	vm->kernel_auto_va.start = auto_kernel_va_start;
@@ -2981,6 +2986,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
 	if (!IS_ALIGNED(op->va | op->size | op->bo_offset, vm_pgsz))
 		return -EINVAL;
 
+	/* We don't allow mappings that overlap with kbo's reserved range */
+	if (range_overflows(op->va, op->size, vm->user_va_range))
+		return -EINVAL;
+
 	switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) {
 	case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP:
 		if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) {

-- 
2.55.0

Re: [PATCH v5 1/2] drm/panthor: Add vm_bind region with kbo range overlap check

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Zero-size asynchronous VM_BIND operations can corrupt the drm_gpuvm interval tree.
--

--- Patch [1]: [PATCH v5 1/2] drm/panthor: Add vm_bind region with kbo range overlap check ---
commit 0c0faa58a385567244a3f75b05f6667907422807
Author: Adrián Larumbe <adrian.larumbe@collabora.com>

drm/panthor: Add vm_bind region with kbo range overlap check

When a VM is created, the caller has to specify the range of the address
space carve-out set aside for mapping kernel buffer objects. That means
vm_bind mappings of userspace-exposed objects should not intersect with
that region, which this patch checks during the vm_bind ioctl.

> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 31cc57029c12c..910c8e579770d 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c

[ ... ]

> @@ -2981,6 +2986,10 @@ panthor_vm_bind_prepare_op_ctx(struct drm_file *file,
>  	if (!IS_ALIGNED(op->va | op->size | op->bo_offset, vm_pgsz))
>  		return -EINVAL;
>  
> +	/* We don't allow mappings that overlap with kbo's reserved range */
> +	if (range_overflows(op->va, op->size, vm->user_va_range))
> +		return -EINVAL;
> +

[Severity: High]
This is a pre-existing issue, but does this function need to reject
op->size == 0 before proceeding?

A zero-size map operation is currently treated as aligned, and
range_overflows() will return false, allowing it to pass this validation.

If userspace passes a zero size, inserting a zero-size interval into the
interval tree will compute an end address of addr - 1. This violates the
red-black augmented tree invariants which require start to be less than
or equal to last.

Could this cause structural corruption of the interval subtree values,
leading to subsequent tree traversals silently failing to find mapped
regions? Unlike the sync path, panthor_vm_bind_job_create() appears to lack
a size check for asynchronous jobs, which might allow unprivileged
userspace to trigger this directly.

>  	switch (op->flags & DRM_PANTHOR_VM_BIND_OP_TYPE_MASK) {
>  	case DRM_PANTHOR_VM_BIND_OP_TYPE_MAP:
>  		if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) {

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260713-vm_bind_checks-v5-0-0d2314af8d9d@collabora.com?part=1

[PATCH v5 2/2] drm/panthor: Fix comment to reflect actual struct field name

[Adrián Larumbe]

The mismatch would pop up when building the kernel with W=1.

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 910c8e579770..3a1b7dcaaf91 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -306,7 +306,7 @@ struct panthor_vm {
 		/** @kernel_auto_va.start: Start of the automatic VA-range for kernel BOs. */
 		u64 start;
 
-		/** @kernel_auto_va.size: Size of the automatic VA-range for kernel BOs. */
+		/** @kernel_auto_va.end: End of the automatic VA-range for kernel BOs. */
 		u64 end;
 	} kernel_auto_va;
 

-- 
2.55.0