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

ira.weiny
2022-10-02T00:23:43Z

From: Ira Weiny <ira.weiny@intel.com>

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 kmap page does slip through warn on once for a kmap address.

Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
drivers/tee/tee_shm.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 527a6eabc03e..45e6ff1a452e 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)
@@ -26,9 +27,9 @@ static int shm_get_kernel_pages(unsigned long start, size_t page_count,
{
struct kvec *kiov;
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);
@@ -38,12 +39,12 @@ static int shm_get_kernel_pages(unsigned long start, size_t page_count,
for (n = 0; n < page_count; n++) {
kiov[n].iov_base = (void *)(start + n * PAGE_SIZE);
kiov[n].iov_len = PAGE_SIZE;
+ pages[n] = virt_to_page(kiov[n].iov_base);
+ 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)
--
2.37.2