[PATCH V1] accel/amdxdna: Fix user buffer VMA checking and page pinning locking

[Lizhi Hou <lizhi.hou@amd.com>]

From: Max Zhen <max.zhen@amd.com>

Holding mmap_read_lock across user buffer VMA checking and page pinning.
This keeps VMA validation and user page pinning synchronized with mmap
updates.

Also adding the check for VM_MAYWRITE to make sure the mapping can't be
updated to writable after pinning of the pages.

Fixes: f649e63d4a64 ("accel/amdxdna: Support read-only user-pointer BO mappings")
Signed-off-by: Max Zhen <max.zhen@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
---
 drivers/accel/amdxdna/amdxdna_ubuf.c | 34 ++++++++++++++++------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/drivers/accel/amdxdna/amdxdna_ubuf.c b/drivers/accel/amdxdna/amdxdna_ubuf.c
index df4ab225fbf9..85c3d6f46845 100644
--- a/drivers/accel/amdxdna/amdxdna_ubuf.c
+++ b/drivers/accel/amdxdna/amdxdna_ubuf.c
@@ -99,17 +99,13 @@ static int readonly_va_entry(struct amdxdna_drm_va_entry *va_ent)
 	struct vm_area_struct *vma;
 	int ret;
 
-	mmap_read_lock(mm);
-
 	vma = find_vma(mm, va_ent->vaddr);
 	if (!vma ||
 	    vma->vm_start > va_ent->vaddr ||
 	    vma->vm_end - va_ent->vaddr < va_ent->len)
 		ret = -ENOENT;
 	else
-		ret = vma->vm_flags & VM_WRITE ? 0 : 1;
-
-	mmap_read_unlock(mm);
+		ret = vma->vm_flags & (VM_WRITE | VM_MAYWRITE) ? 0 : 1;
 	return ret;
 }
 
@@ -123,7 +119,7 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,
 	u32 npages, start = 0;
 	struct dma_buf *dbuf;
 	bool readonly = true;
-	int i, ret;
+	int i, ret = 0;
 	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
 
 	if (!can_do_mlock())
@@ -161,10 +157,6 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,
 			ret = -EINVAL;
 			goto free_ent;
 		}
-
-		/* Pin pages as writable as long as not all entries are read-only. */
-		if (readonly && readonly_va_entry(&va_ent[i]) != 1)
-			readonly = false;
 	}
 
 	ubuf->nr_pages = exp_info.size >> PAGE_SHIFT;
@@ -183,25 +175,37 @@ struct dma_buf *amdxdna_get_ubuf(struct drm_device *dev,
 		goto sub_pin_cnt;
 	}
 
+	mmap_read_lock(current->mm);
+
+	for (i = 0; i < num_entries; i++) {
+		/* Pin pages as writable as long as not all entries are read-only. */
+		if (readonly && readonly_va_entry(&va_ent[i]) != 1)
+			readonly = false;
+	}
 	for (i = 0; i < num_entries; i++) {
 		npages = va_ent[i].len >> PAGE_SHIFT;
 
-		ret = pin_user_pages_fast(va_ent[i].vaddr, npages,
-					  (readonly ? 0 : FOLL_WRITE) | FOLL_LONGTERM,
-					  &ubuf->pages[start]);
+		ret = pin_user_pages(va_ent[i].vaddr, npages,
+				     (readonly ? 0 : FOLL_WRITE) | FOLL_LONGTERM,
+				     &ubuf->pages[start]);
 		if (ret >= 0) {
 			start += ret;
 			if (ret != npages) {
 				XDNA_ERR(xdna, "Partially pinned pages %d/%u", ret, npages);
 				ret = -ENOMEM;
-				goto destroy_pages;
+				break;
 			}
 		} else {
 			XDNA_ERR(xdna, "Failed to pin pages ret %d", ret);
-			goto destroy_pages;
+			break;
 		}
 	}
 
+	mmap_read_unlock(current->mm);
+
+	if (ret < 0)
+		goto destroy_pages;
+
 	exp_info.ops = &amdxdna_ubuf_dmabuf_ops;
 	exp_info.priv = ubuf;
 	exp_info.flags = (readonly ? O_RDONLY : O_RDWR) | O_CLOEXEC;
-- 
2.34.1