On 06/21/2010 03:55 PM, 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?
Looks good to me.
Thanks
Prasanna
Thanks,
NeilBrown
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index aa9f7b6..0334655 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) {
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)) {
@@ -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--;
---
drivers/md/raid10.c | 51 +++++++++++++++++++++++++++------------------------
1 files changed, 27 insertions(+), 24 deletions(-)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0372499..9556faa 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1490,31 +1490,34 @@ static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
int cur_read_error_count = 0;
rdev = rcu_dereference(conf->mirrors[d].rdev);
- bdevname(rdev->bdev, b);
+ if (rdev) { /* Check if the mirror raid device is not NULL*/
+ bdevname(rdev->bdev, b);
- if (test_bit(Faulty,&rdev->flags)) {
- rcu_read_unlock();
- /* drive has already been failed, just ignore any
- more fix_read_error() attempts */
- return;
- }
+ if (test_bit(Faulty,&rdev->flags)) {
+ rcu_read_unlock();
+ /* drive has already been failed, just ignore
+ any more fix_read_error() attempts */
+ return;
+ }
- check_decay_read_errors(mddev, rdev);
- atomic_inc(&rdev->read_errors);
- cur_read_error_count = atomic_read(&rdev->read_errors);
- if (cur_read_error_count> max_read_errors) {
- rcu_read_unlock();
- printk(KERN_NOTICE
- "md/raid10:%s: %s: Raid device exceeded "
- "read_error threshold "
- "[cur %d:max %d]\n",
- mdname(mddev),
- b, cur_read_error_count, max_read_errors);
- printk(KERN_NOTICE
- "md/raid10:%s: %s: Failing raid "
- "device\n", mdname(mddev), b);
- md_error(mddev, conf->mirrors[d].rdev);
- return;
+ check_decay_read_errors(mddev, rdev);
+ atomic_inc(&rdev->read_errors);
+ cur_read_error_count = atomic_read(&rdev->read_errors);
+ if (cur_read_error_count> max_read_errors) {
+ rcu_read_unlock();
+ printk(KERN_NOTICE
+ "md/raid10:%s: %s: Raid device exceeded "
+ "read_error threshold "
+ "[cur %d:max %d]\n",
+ mdname(mddev),
+ b, cur_read_error_count,
+ max_read_errors);
+ printk(KERN_NOTICE
+ "md/raid10:%s: %s: Failing raid "
+ "device\n", mdname(mddev), b);
+ md_error(mddev, conf->mirrors[d].rdev);
+ return;
+ }
}
}
rcu_read_unlock();
--
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