From: Li Nan linan122@huawei.com
hulk inclusion category: bugfix bugzilla: 188787, https://gitee.com/openeuler/kernel/issues/I78YIW CVE: NA
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When we remove a disk which has replacement, first set rdev to NULL and then set replacement to rdev, finally set replacement to NULL (see raid10_remove_disk()). If io is submitted during the same time, it might read both rdev and replacement as NULL, and io will not be submitted.
rdev -> NULL read rdev replacement -> NULL read replacement
Fix it by reading replacement first and rdev later, meanwhile, use smp_mb() to prevent memory reordering.
Fixes: 475b0321a4df ("md/raid10: writes should get directed to replacement as well as original.") Signed-off-by: Li Nan linan122@huawei.com Reviewed-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Hou Tao houtao1@huawei.com --- drivers/md/raid10.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-)
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 2c41b201cfb4..e04182abfb08 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -754,8 +754,16 @@ static struct md_rdev *read_balance(struct r10conf *conf, rdev = rcu_dereference(conf->mirrors[disk].replacement); if (rdev == NULL || test_bit(Faulty, &rdev->flags) || test_bit(WantRemove, &rdev->flags) || - r10_bio->devs[slot].addr + sectors > rdev->recovery_offset) + r10_bio->devs[slot].addr + sectors > + rdev->recovery_offset) { + /* + * Read replacement first to prevent reading both rdev + * and replacement as NULL during replacement replace + * rdev + */ + smp_mb(); rdev = rcu_dereference(conf->mirrors[disk].rdev); + } if (rdev == NULL || test_bit(WantRemove, &rdev->flags) || test_bit(Faulty, &rdev->flags)) @@ -1363,9 +1371,15 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
for (i = 0; i < conf->copies; i++) { int d = r10_bio->devs[i].devnum; - struct md_rdev *rdev = rcu_dereference(conf->mirrors[d].rdev); - struct md_rdev *rrdev = rcu_dereference( - conf->mirrors[d].replacement); + struct md_rdev *rrdev, *rdev; + + rrdev = rcu_dereference(conf->mirrors[d].replacement); + /* + * Read replacement first to Prevent reading both rdev and + * replacement as NULL during replacement replace rdev. + */ + smp_mb(); + rdev = rcu_dereference(conf->mirrors[d].rdev); if (rdev == rrdev) rrdev = NULL; if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {