[PATCH v2 3/4] tee: Remove call to get_kernel_pages()

[Ira Weiny]

The kernel pages used by shm_get_kernel_pages() are allocated using
GFP_KERNEL through the following call stack:

trusted_instantiate()
	trusted_payload_alloc() -> GFP_KERNEL
	<trusted key op>
		tee_shm_register_kernel_buf()
			register_shm_helper()
				shm_get_kernel_pages()

Where <trusted key op> is one of:

	trusted_key_unseal()
	trusted_key_get_random()
	trusted_key_seal()

Because the pages can't be from highmem get_kernel_pages() boils down to
a get_page() call.

Remove the get_kernel_pages() call and open code the get_page().

In case a highmem page does slip through warn on once for a kmap'ed
address.

Cc: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "Fabio M. De Francesco" <fmdefrancesco@xxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes from v1:
	Al/Christoph: Remove kiov altogether
---
 drivers/tee/tee_shm.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 527a6eabc03e..b1c6231defad 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -11,6 +11,7 @@
 #include <linux/tee_drv.h>
 #include <linux/uaccess.h>
 #include <linux/uio.h>
+#include <linux/highmem.h>
 #include "tee_private.h"
 
 static void shm_put_kernel_pages(struct page **pages, size_t page_count)
@@ -24,26 +25,20 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count)
 static int shm_get_kernel_pages(unsigned long start, size_t page_count,
 				struct page **pages)
 {
-	struct kvec *kiov;
+	struct page *page;
 	size_t n;
-	int rc;
 
-	if (WARN_ON_ONCE(is_vmalloc_addr((void *)start)))
+	if (WARN_ON_ONCE(is_vmalloc_addr((void *)start) ||
+			 is_kmap_addr((void *)start)))
 		return -EINVAL;
 
-	kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL);
-	if (!kiov)
-		return -ENOMEM;
-
+	page = virt_to_page(start);
 	for (n = 0; n < page_count; n++) {
-		kiov[n].iov_base = (void *)(start + n * PAGE_SIZE);
-		kiov[n].iov_len = PAGE_SIZE;
+		pages[n] = page + n;
+		get_page(pages[n]);
 	}
 
-	rc = get_kernel_pages(kiov, page_count, 0, pages);
-	kfree(kiov);
-
-	return rc;
+	return page_count;
 }
 
 static void release_registered_pages(struct tee_shm *shm)

-- 
2.39.1