[PATCH] drm/amdgpu: fix userq page count in input_validate

[Zhu Lingshan <lingshan.zhu@amd.com>]

amdgpu_userq_input_va_validate() converts userq
expected_size to page count by right shift.

This undercounts va buffers that less than a page.
For example, in the AMDGPU_HW_IP_COMPUTE userq
creation case, the expected_size 2048,
so size(page count) becomes zero page and the
"va_map->last - user_addr + 1 >= size" is always true
once the start addr locates in the va_map mapping.

A similar case is AMDGPU_HW_IP_DMA, where expected_size is 32.

This commit calculates a proper page count by subtracting
the start_addr and end_addr in pages.

Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
index 969f49592450..f9f11bdf2cef 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.c
@@ -25,6 +25,7 @@
 #include <drm/drm_auth.h>
 #include <drm/drm_exec.h>
 #include <linux/pm_runtime.h>
+#include <linux/overflow.h>
 #include <drm/drm_drv.h>
 
 #include "amdgpu.h"
@@ -238,14 +239,21 @@ int amdgpu_userq_input_va_validate(struct amdgpu_device *adev,
 {
 	struct amdgpu_bo_va_mapping *va_map;
 	struct amdgpu_vm *vm = queue->vm;
-	u64 user_addr;
+	u64 user_addr, end;
 	u64 size;
 
 	/* Caller must hold vm->root.bo reservation */
 	dma_resv_assert_held(queue->vm->root.bo->tbo.base.resv);
 
-	user_addr = (addr & AMDGPU_GMC_HOLE_MASK) >> AMDGPU_GPU_PAGE_SHIFT;
-	size = expected_size >> AMDGPU_GPU_PAGE_SHIFT;
+	if (!expected_size)
+		return -EINVAL;
+
+	user_addr = addr & AMDGPU_GMC_HOLE_MASK;
+	if (check_add_overflow(user_addr, expected_size - 1, &end))
+		return -EINVAL;
+
+	user_addr >>= AMDGPU_GPU_PAGE_SHIFT;
+	size = (end >> AMDGPU_GPU_PAGE_SHIFT) - user_addr + 1;
 
 	va_map = amdgpu_vm_bo_lookup_mapping(vm, user_addr);
 	if (!va_map)
-- 
2.53.0