[PATCH] staging: vchiq_2835_arm: Fix NULL ptr dereference in free_pagelist

[Stefan Wahren]

This fixes a NULL pointer dereference on RPi 2 with multi_v7_defconfig.
The function page_address() could return NULL with enabled CONFIG_HIGHMEM.
So fix this by using kmap() instead.

Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
Fixes: 71bad7f08641 ("staging: add bcm2708 vchiq driver")
---
 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
index 0159ca4..be08849 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
@@ -612,18 +612,20 @@ free_pagelist(struct vchiq_pagelist_info *pagelistinfo,
 			if (head_bytes > actual)
 				head_bytes = actual;
 
-			memcpy((char *)page_address(pages[0]) +
+			memcpy((char *)kmap(pages[0]) +
 				pagelist->offset,
 				fragments,
 				head_bytes);
+			kunmap(pages[0]);
 		}
 		if ((actual >= 0) && (head_bytes < actual) &&
 			(tail_bytes != 0)) {
-			memcpy((char *)page_address(pages[num_pages - 1]) +
+			memcpy((char *)kmap(pages[num_pages - 1]) +
 				((pagelist->offset + actual) &
 				(PAGE_SIZE - 1) & ~(g_cache_line_size - 1)),
 				fragments + g_cache_line_size,
 				tail_bytes);
+			kunmap(pages[num_pages - 1]);
 		}
 
 		down(&g_free_fragments_mutex);
-- 
2.7.4