[PATCH] target: Explicitly clear ramdisk_mcp backend pages

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From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>

Hi Greg,

Please apply the following patch to stable, as it addresses a potential
security issue as reported by Jorge.

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 is a one-liner that addresses the bug for all <= v3.14 versions.

Please apply.

Thanks,

--nab

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

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@xxxxxxxxxxxxxxxxxx>
Cc: Jorge Daniel Sequeira Matias <jdsm@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
 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 b920db3..7b331b9 100644
--- a/drivers/target/target_core_rd.c
+++ b/drivers/target/target_core_rd.c
@@ -158,7 +158,7 @@ static int rd_allocate_sgl_table(struct rd_dev *rd_dev, struct rd_dev_sg_table *
 						- 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");
-- 
1.8.5.3

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