Patch "staging: vc04_services: Fix bulk cache maintenance" has been added to the 4.11-stable tree

This is a note to let you know that I've just added the patch titled

staging: vc04_services: Fix bulk cache maintenance

to the 4.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
staging-vc04_services-fix-bulk-cache-maintenance.patch
and it can be found in the queue-4.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Phil Elwell <[email protected]>
Date: Thu, 4 May 2017 10:58:20 +0100
Subject: staging: vc04_services: Fix bulk cache maintenance

From: Phil Elwell <[email protected]>

commit ff92b9e3c9f85fa442c430d70bf075499e1193b7 upstream.

vchiq_arm supports transfers less than one page and at arbitrary alignment, using the dma-mapping API to perform its cache maintenance (even though the VPU drives the DMA hardware). Read (DMA_FROM_DEVICE) operations use cache invalidation for speed, falling back to clean+invalidate on partial cache lines, with writes (DMA_TO_DEVICE) using flushes.

If a read transfer has ends which aren't page-aligned, performing cache maintenance as if they were whole pages can lead to memory corruption since the partial cache lines at the ends (and any cache lines before or after the transfer area) will be invalidated. This bug was masked until the disabling of the cache flush in flush_dcache_page().

Honouring the requested transfer start- and end-points prevents the corruption.

---
 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c |   31 ++++++----
 1 file changed, 19 insertions(+), 12 deletions(-)

@@ -501,8 +501,15 @@ create_pagelist(char __user *buf, size_t
 	 */
 	sg_init_table(scatterlist, num_pages);
 	/* Now set the pages for each scatterlist */
-	for (i = 0; i < num_pages; i++)
-		sg_set_page(scatterlist + i, pages[i], PAGE_SIZE, 0);
+	for (i = 0; i < num_pages; i++)	{
+		unsigned int len = PAGE_SIZE - offset;
+
+		if (len > count)
+			len = count;
+		sg_set_page(scatterlist + i, pages[i], len, offset);
+		offset = 0;
+		count -= len;
+	}
 
 	dma_buffers = dma_map_sg(g_dev,
 				 scatterlist,

@@ -523,20 +530,20 @@ create_pagelist(char __user *buf, size_t
 		u32 addr = sg_dma_address(sg);
 
 		/* Note: addrs is the address + page_count - 1
-		 * The firmware expects the block to be page
+		 * The firmware expects blocks after the first to be page-
 		 * aligned and a multiple of the page size
 		 */
 		WARN_ON(len == 0);
-		WARN_ON(len & ~PAGE_MASK);
-		WARN_ON(addr & ~PAGE_MASK);
+		WARN_ON(i && (i != (dma_buffers - 1)) && (len & ~PAGE_MASK));
+		WARN_ON(i && (addr & ~PAGE_MASK));
 		if (k > 0 &&
-		    ((addrs[k - 1] & PAGE_MASK) |
-			((addrs[k - 1] & ~PAGE_MASK) + 1) << PAGE_SHIFT)
-		    == addr) {
-			addrs[k - 1] += (len >> PAGE_SHIFT);
-		} else {
-			addrs[k++] = addr | ((len >> PAGE_SHIFT) - 1);
-		}
+		    ((addrs[k - 1] & PAGE_MASK) +
+		     (((addrs[k - 1] & ~PAGE_MASK) + 1) << PAGE_SHIFT))
+		    == (addr & PAGE_MASK))
+			addrs[k - 1] += ((len + PAGE_SIZE - 1) >> PAGE_SHIFT);
+		else
+			addrs[k++] = (addr & PAGE_MASK) |
+				(((len + PAGE_SIZE - 1) >> PAGE_SHIFT) - 1);
 	}
 
 	/* Partial cache lines (fragments) require special measures */

Patches currently in stable-queue which might be from [email protected] are

queue-4.11/staging-vc04_services-fix-bulk-cache-maintenance.patch