Commit 16e993ac authored Apr 08, 2022 by Xiaomeng Tong Committed by Greg Kroah-Hartman Jun 14, 2022

md: fix an incorrect NULL check in md_reload_sb



commit 64c54d9244a4efe9bc6e9c98e13c4bbb8bb39083 upstream.

The bug is here:
	if (!rdev || rdev->desc_nr != nr) {

The list iterator value 'rdev' will *always* be set and non-NULL
by rdev_for_each_rcu(), so it is incorrect to assume that the
iterator value will be NULL if the list is empty or no element
found (In fact, it will be a bogus pointer to an invalid struct
object containing the HEAD). Otherwise it will bypass the check
and lead to invalid memory access passing the check.

To fix the bug, use a new variable 'iter' as the list iterator,
while using the original variable 'pdev' as a dedicated pointer to
point to the found element.

Cc: stable@vger.kernel.org
Fixes: 70bcecdb ("md-cluster: Improve md_reload_sb to be less error prone")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d0bdc809

drivers/md/md.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -9531,16 +9531,18 @@ static int read_rdev(struct mddev mddev, struct md_rdev rdev)

		void md_reload_sb(struct mddev *mddev, int nr)
		{
		struct md_rdev *rdev;
		struct md_rdev rdev = NULL, iter;
		int err;

		/* Find the rdev */
		rdev_for_each_rcu(rdev, mddev) {
		if (rdev->desc_nr == nr)
		rdev_for_each_rcu(iter, mddev) {
		if (iter->desc_nr == nr) {
		rdev = iter;
		break;
		}
		}

		if (!rdev \|\| rdev->desc_nr != nr) {
		if (!rdev) {
		pr_warn("%s: %d Could not find rdev with nr %d\n", __func__, __LINE__, nr);
		return;
		}