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Date: Tue, 7 Jun 2022 19:04:21 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Xiaomeng Tong <xiam0nd.tong@...il.com>, Song Liu <song@...nel.org> Subject: [PATCH 5.15 596/667] md: fix an incorrect NULL check in md_reload_sb From: Xiaomeng Tong <xiam0nd.tong@...il.com> 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@...r.kernel.org Fixes: 70bcecdb1534 ("md-cluster: Improve md_reload_sb to be less error prone") Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com> Signed-off-by: Song Liu <song@...nel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- drivers/md/md.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9774,16 +9774,18 @@ static int read_rdev(struct mddev *mddev 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; }
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