linux-kernel - [PATCH 3/4] tee: Remove call to get_kernel

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Date:   Sat,  1 Oct 2022 17:23:25 -0700
From:   ira.weiny@...el.com
To:     Jens Wiklander <jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Ira Weiny <ira.weiny@...el.com>, Al Viro <viro@...iv.linux.org.uk>,
        "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Christoph Hellwig <hch@....de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        op-tee@...ts.trustedfirmware.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH 3/4] tee: Remove call to get_kernel_pages()

From: Ira Weiny <ira.weiny@...el.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@...aro.org>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: "Fabio M. De Francesco" <fmdefrancesco@...il.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ira Weiny <ira.weiny@...el.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