target: Explicitly clear ramdisk_mcp backend pages

[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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/target/target_core_rd.c b/drivers/target/target_core_rd.c
index 0921a64b555028997691fb28ad7ab84294b10a0d..5c3b6778c22a3b30ce838a7849844b88c31af16d 100644 (file)
--- 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");