| Message ID | 20220328080559.25984-1-xiam0nd.tong@gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | md: fix an incorrect NULL check in md_reload_sb | expand |
On Mon, Mar 28, 2022 at 1:06 AM Xiaomeng Tong <xiam0nd.tong@gmail.com> wrote: > > 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: 70bcecdb1534 ("amd-cluster: Improve md_reload_sb to be less error prone") s/amd-cluster/md-cluster/ > Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> > --- > > changes from v1: > - rephrase the subject (Guoqing Jiang) > > v1:https://lore.kernel.org/lkml/20220327080111.12028-1-xiam0nd.tong@gmail.com/ > > --- > drivers/md/md.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 7476fc204172..f156678c08bc 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -9794,16 +9794,18 @@ 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; > } > -- > 2.17.1 >
diff --git a/drivers/md/md.c b/drivers/md/md.c index 7476fc204172..f156678c08bc 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9794,16 +9794,18 @@ 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; }
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: 70bcecdb1534 ("amd-cluster: Improve md_reload_sb to be less error prone") Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com> --- changes from v1: - rephrase the subject (Guoqing Jiang) v1:https://lore.kernel.org/lkml/20220327080111.12028-1-xiam0nd.tong@gmail.com/ --- drivers/md/md.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)