[PATCH 3.8 06/13] target: Explicitly clear ramdisk_mcp backend pages

[Kamal Mostafa]

3.8.13.28 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Bellinger <nab at linux-iscsi.org>

[Note that a different patch to address the same issue went in during
v3.15-rc1 (commit 4442dc8a), but includes a bunch of other changes that
don't strictly apply to fixing the bug.]

This patch changes rd_allocate_sgl_table() to explicitly clear
ramdisk_mcp backend memory pages by passing __GFP_ZERO into
alloc_pages().

This addresses a potential security issue where reading from a
ramdisk_mcp could return sensitive information, and follows what
>= v3.15 does to explicitly clear ramdisk_mcp memory at backend
device initialization time.

Reported-by: Jorge Daniel Sequeira Matias <jdsm at tecnico.ulisboa.pt>
Cc: Jorge Daniel Sequeira Matias <jdsm at tecnico.ulisboa.pt>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
Reference: CVE-2014-4027
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/target/target_core_rd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
index 0457de3..51968ed 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -174,7 +174,7 @@ static int rd_build_device_space(struct rd_dev *rd_dev)
 						- 1;
 
 		for (j = 0; j < sg_per_table; j++) {
-			pg = alloc_pages(GFP_KERNEL, 0);
+			pg = alloc_pages(GFP_KERNEL | __GFP_ZERO, 0);
 			if (!pg) {
 				pr_err("Unable to allocate scatterlist"
 					" pages for struct rd_dev_sg_table\n");
-- 
1.9.1