On Tue, 22 Jun 2010 19:40:47 -0700
"Prasanna S. Panchamukhi" <prasanna.panchamukhi@xxxxxxxxxxxx> wrote:
> On Mon, Jun 21, 2010 at 03:55:41PM -0700, Neil Brown wrote:
> > On Mon, 21 Jun 2010 15:14:35 -0700
> > prasanna.panchamukhi@xxxxxxxxxxxx wrote:
> >
> > > From: Prasanna S. Panchamukhi <prasanna.panchamukhi@xxxxxxxxxxxx>
> > >
> > > Such NULL pointer dereference can occur when the driver was fixing the
> > > read errors/bad blocks and the disk was physically removed
> > > causing a system crash. This patch check if the
> > > rcu_dereference() returns valid rdev before accessing it in fix_read_error().
> > >
> > > Signed-off-by: Prasanna S. Panchamukhi <prasanna.panchamukhi@xxxxxxxxxxxx>
> > > Signed-off-by: Rob Becker <rbecker@xxxxxxxxxxxx>
> >
> > Thanks for the patch.
> > However all that extra indenting is rather painful - and we already have more
> > than we should.
> >
> > How about this instead?
>
> Hi Neil,
>
> Thanks for your review, Please find the updated patch as per your suggestion
> below.
Thanks. You even found a "int d;" to remove that I had missed.
I've added you patch you my queue. It will go into -testing and then to
Linus in due course.
I have added "cc: stable@xxxxxxxxxx" so that it gets included -stable
releases.
Thanks,
NeilBrown
>
> Thanks
> Prasanna
>
> >From c2bb6a02707335430d31dc901093108cc6046af2 Mon Sep 17 00:00:00 2001
> From: Prasanna S. Panchamukhi <prasanna.panchamukhi@xxxxxxxxxxxx>
> Date: Tue, 22 Jun 2010 18:59:33 -0700
> Subject: [PATCH] drivers/md: raid10: Fix null pointer dereference in fix_read_error()
>
> Such NULL pointer dereference can occur when the driver was fixing the
> read errors/bad blocks and the disk was physically removed
> causing a system crash. This patch check if the
> rcu_dereference() returns valid rdev before accessing it in fix_read_error().
>
> Signed-off-by: Prasanna S. Panchamukhi <prasanna.panchamukhi@xxxxxxxxxxxx>
> Signed-off-by: Rob Becker <rbecker@xxxxxxxxxxxx>
> ---
> drivers/md/raid10.c | 12 ++++++------
> 1 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 0372499..6d420cb 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -1482,14 +1482,14 @@ static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
> int sectors = r10_bio->sectors;
> mdk_rdev_t*rdev;
> int max_read_errors = atomic_read(&mddev->max_corr_read_errors);
> + int d = r10_bio->devs[r10_bio->read_slot].devnum;
>
> rcu_read_lock();
> - {
> - int d = r10_bio->devs[r10_bio->read_slot].devnum;
> + rdev = rcu_dereference(conf->mirrors[d].rdev);
> + if (rdev) { /* If rdev is not NULL */
> char b[BDEVNAME_SIZE];
> int cur_read_error_count = 0;
>
> - rdev = rcu_dereference(conf->mirrors[d].rdev);
> bdevname(rdev->bdev, b);
>
> if (test_bit(Faulty, &rdev->flags)) {
> @@ -1530,7 +1530,7 @@ static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
>
> rcu_read_lock();
> do {
> - int d = r10_bio->devs[sl].devnum;
> + d = r10_bio->devs[sl].devnum;
> rdev = rcu_dereference(conf->mirrors[d].rdev);
> if (rdev &&
> test_bit(In_sync, &rdev->flags)) {
> @@ -1564,7 +1564,7 @@ static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
> rcu_read_lock();
> while (sl != r10_bio->read_slot) {
> char b[BDEVNAME_SIZE];
> - int d;
> +
> if (sl==0)
> sl = conf->copies;
> sl--;
> @@ -1601,7 +1601,7 @@ static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
> }
> sl = start;
> while (sl != r10_bio->read_slot) {
> - int d;
> +
> if (sl==0)
> sl = conf->copies;
> sl--;
--
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