Re: md: raid10: fix use-after-free of bio

On Monday July 30, m.hampel@gmx.de wrote:

quoted

Surely we just leaked that bio if (mirror == -1)?

better:

--- a/drivers/md/raid10.c~md-raid10-fix-use-after-free-of-bio
+++ a/drivers/md/raid10.c

@@ -1534,7 +1534,6 @@ static void raid10d(mddev_t *mddev)
 			bio = r10_bio->devs[r10_bio->read_slot].bio;
 			r10_bio->devs[r10_bio->read_slot].bio =
 				mddev->ro ? IO_BLOCKED : NULL;
-			bio_put(bio);
 			mirror = read_balance(conf, r10_bio);
 			if (mirror == -1) {
 				printk(KERN_ALERT "raid10: %s: unrecoverable I/O"

@@ -1542,8 +1541,10 @@ static void raid10d(mddev_t *mddev)
 				       bdevname(bio->bi_bdev,b),
 				       (unsigned long long)r10_bio->sector);
 				raid_end_bio_io(r10_bio);
+				bio_put(bio);

raid_end_bio_io() calls put_all_bios(), which does a bio_put() to
corresponding r10_bio->devs[i]. So this looks like redundant code for
me.

Yes, but note above that this bio for this slot has been set to
'NULL', so put_all_bios won't find anything to call bio_put on.

Thanks,
NeilBrown

quoted

 			} else {
 				const int do_sync = bio_sync(r10_bio->master_bio);
+				bio_put(bio);
 				rdev = conf->mirrors[mirror].rdev;
 				if (printk_ratelimit())
 					printk(KERN_ERR "raid10: %s: redirecting sector %llu to"

Regards, 
Maik Hampel