release/5.2.29/md-raid10-prevent-access-of-uninitialized-resync_pag.patch

From 1096884e8a19b194bb43724e9e7edde69b71addb Mon Sep 17 00:00:00 2001
From: John Pittman <jpittman@redhat.com>
Date: Mon, 11 Nov 2019 16:43:20 -0800
Subject: [PATCH] md/raid10: prevent access of uninitialized resync_pages
 offset

commit 45422b704db392a6d79d07ee3e3670b11048bd53 upstream.

Due to unneeded multiplication in the out_free_pages portion of
r10buf_pool_alloc(), when using a 3-copy raid10 layout, it is
possible to access a resync_pages offset that has not been
initialized.  This access translates into a crash of the system
within resync_free_pages() while passing a bad pointer to
put_page().  Remove the multiplication, preventing access to the
uninitialized area.

Fixes: f0250618361db ("md: raid10: don't use bio's vec table to manage resync pages")
Cc: stable@vger.kernel.org # 4.12+
Signed-off-by: John Pittman <jpittman@redhat.com>
Suggested-by: David Jeffery <djeffery@redhat.com>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index aea11476fee6..57e2a4e8659a 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -221,7 +221,7 @@ static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
 
 out_free_pages:
 	while (--j >= 0)
-		resync_free_pages(&rps[j * 2]);
+		resync_free_pages(&rps[j]);
 
 	j = 0;
 out_free_bio:
-- 
2.7.4