diff options
Diffstat (limited to 'block/genhd.c')
| -rw-r--r-- | block/genhd.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/block/genhd.c b/block/genhd.c index 27511b3d164d..af6cba2a9332 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -344,11 +344,12 @@ static inline int sector_in_part(struct hd_struct *part, sector_t sector) * primarily used for stats accounting. * * CONTEXT: - * RCU read locked. The returned partition pointer is valid only - * while preemption is disabled. + * RCU read locked. The returned partition pointer is always valid + * because its refcount is grabbed. * * RETURNS: * Found partition on success, part0 is returned if no partition matches + * or the matched partition is being deleted. */ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector) { @@ -359,17 +360,25 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector) ptbl = rcu_dereference(disk->part_tbl); part = rcu_dereference(ptbl->last_lookup); - if (part && sector_in_part(part, sector)) + if (part && sector_in_part(part, sector) && hd_struct_try_get(part)) return part; for (i = 1; i < ptbl->len; i++) { part = rcu_dereference(ptbl->part[i]); if (part && sector_in_part(part, sector)) { + /* + * only live partition can be cached for lookup, + * so use-after-free on cached & deleting partition + * can be avoided + */ + if (!hd_struct_try_get(part)) + break; rcu_assign_pointer(ptbl->last_lookup, part); return part; } } + hd_struct_get(&disk->part0); return &disk->part0; } |