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authorMing Lei <ming.lei@redhat.com>2020-05-08 16:17:55 +0800
committerJens Axboe <axboe@kernel.dk>2020-05-12 20:31:39 -0600
commitb7d6c30333239f77f8e51423064a623acc7fd127 (patch)
tree0f40462c0e231e405291ed5a2c32e0f9d6795ada /block/partitions
parentaa880ad690ab6d4c53934af85fb5a43e69ecb0f5 (diff)
block: fix use-after-free on cached last_lookup partition
delete_partition() clears the cached last_lookup partition. However the .last_lookup cache may be overwritten by one IO path after it is cleared from delete_partition(). Then another IO path may use the cached deleting partition after hd_struct_free() is called, then use-after-free is triggered on the cached partition. Fixes the issue by the following approach: 1) always get the partition's refcount via hd_struct_try_get() before setting .last_lookup 2) move clearing .last_lookup from delete_partition() to hd_struct_free() which is the release handle of the partition's percpu-refcount, so that no IO path can cache deleteing partition via .last_lookup. It is one candidate approach of Yufen's patch[1] which adds overhead in fast path by indirect lookup which may introduce one extra cacheline in IO path. Also this patch relies on percpu-refcount's protection, and it is easier to understand and verify. [1] https://lore.kernel.org/linux-block/20200109013551.GB9655@ming.t460p/T/#t Reported-by: Yufen Yu <yuyufen@huawei.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@infradead.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Hou Tao <houtao1@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/partitions')
-rw-r--r--block/partitions/core.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 873999e2e2f2..8d8c87207fc2 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -288,6 +288,12 @@ static void hd_struct_free_work(struct work_struct *work)
static void hd_struct_free(struct percpu_ref *ref)
{
struct hd_struct *part = container_of(ref, struct hd_struct, ref);
+ struct gendisk *disk = part_to_disk(part);
+ struct disk_part_tbl *ptbl =
+ rcu_dereference_protected(disk->part_tbl, 1);
+
+ rcu_assign_pointer(ptbl->last_lookup, NULL);
+ put_device(disk_to_dev(disk));
INIT_RCU_WORK(&part->rcu_work, hd_struct_free_work);
queue_rcu_work(system_wq, &part->rcu_work);
@@ -309,8 +315,12 @@ void delete_partition(struct gendisk *disk, struct hd_struct *part)
struct disk_part_tbl *ptbl =
rcu_dereference_protected(disk->part_tbl, 1);
+ /*
+ * ->part_tbl is referenced in this part's release handler, so
+ * we have to hold the disk device
+ */
+ get_device(disk_to_dev(part_to_disk(part)));
rcu_assign_pointer(ptbl->part[part->partno], NULL);
- rcu_assign_pointer(ptbl->last_lookup, NULL);
kobject_put(part->holder_dir);
device_del(part_to_dev(part));