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md: fix an incorrect NULL check in does_sb_need_changing

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commit fc8738343eefc4ea8afb6122826dea48eacde514 upstream.

The bug is here:
	if (!rdev)

The list iterator value 'rdev' will *always* be set and non-NULL
by rdev_for_each(), so it is incorrect to assume that the iterator
value will be NULL if the list is empty or no element found.
Otherwise it will bypass the NULL 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 'rdev' as a dedicated pointer to
point to the found element.

Cc: stable@vger.kernel.org
Fixes: 2aa82191ac36 ("md-cluster: Perform a lazy update")
Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Acked-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xiaomeng Tong 2022-04-08 16:37:28 +08:00 committed by Greg Kroah-Hartman
parent 35511d4fdd
commit 7907930218
1 changed files with 5 additions and 3 deletions
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8
drivers/md/md.c
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@ -2628,14 +2628,16 @@ static void sync_sbs(struct mddev *mddev, int nospares)
static bool does_sb_need_changing(struct mddev *mddev)
{
struct md_rdev *rdev;
struct md_rdev *rdev = NULL, *iter;
struct mdp_superblock_1 *sb;
int role;
/* Find a good rdev */
rdev_for_each(rdev, mddev)
if ((rdev->raid_disk >= 0) && !test_bit(Faulty, &rdev->flags))
rdev_for_each(iter, mddev)
if ((iter->raid_disk >= 0) && !test_bit(Faulty, &iter->flags)) {
rdev = iter;
break;
}
/* No good device found. */
if (!rdev)