[PATCH 3.12 157/181] target: Explicitly clear ramdisk_mcp backend pages

Jiri Slaby
2014-06-30T12:30:53Z

From: "Nicholas A. Bellinger" <nab@linux-iscsi.org>

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

===============

[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@tecnico.ulisboa.pt>
Cc: Jorge Daniel Sequeira Matias <jdsm@tecnico.ulisboa.pt>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
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 131327ac7f5b..9f6bedecda6e 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -179,7 +179,7 @@ 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");
--
2.0.0