linux-kernel - [PATCH 4.19 260/306] md/raid10: prevent access of uninitialized resync

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Message-Id: <20191127203133.828677762@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:31:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, John Pittman <jpittman@...hat.com>,
        David Jeffery <djeffery@...hat.com>,
        Laurence Oberman <loberman@...hat.com>,
        Song Liu <songliubraving@...com>
Subject: [PATCH 4.19 260/306] md/raid10: prevent access of uninitialized resync_pages offset

From: John Pittman <jpittman@...hat.com>

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@...r.kernel.org # 4.12+
Signed-off-by: John Pittman <jpittman@...hat.com>
Suggested-by: David Jeffery <djeffery@...hat.com>
Reviewed-by: Laurence Oberman <loberman@...hat.com>
Signed-off-by: Song Liu <songliubraving@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/raid10.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -229,7 +229,7 @@ static void * r10buf_pool_alloc(gfp_t gf
 
 out_free_pages:
 	while (--j >= 0)
-		resync_free_pages(&rps[j * 2]);
+		resync_free_pages(&rps[j]);
 
 	j = 0;
 out_free_bio: