md/raid10: prevent access of uninitialized resync_pages offset

BugLink: https://bugs.launchpad.net/bugs/1854975
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index a200c5dfd9d605fe482483d81d03d5892a05e49a..667ec57debaa28fe7cef0fc042a4af2616428d3d 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -229,7 +229,7 @@ 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: