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md: fix an incorrect NULL check in md_reload_sb

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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: 70bcecdb15 ("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>
This commit is contained in:
Xiaomeng Tong 2022-04-08 16:47:15 +08:00 committed by Song Liu
parent fc8738343e
commit 64c54d9244
1 changed files with 6 additions and 4 deletions
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10
drivers/md/md.c
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@ -9795,16 +9795,18 @@ 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;
}