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authorMing Lei <ming.lei@redhat.com>2020-05-08 11:17:55 +0300
committerJens Axboe <axboe@kernel.dk>2020-05-13 05:31:39 +0300
commitb7d6c30333239f77f8e51423064a623acc7fd127 (patch)
tree0f40462c0e231e405291ed5a2c32e0f9d6795ada /block/blk-core.c
parentaa880ad690ab6d4c53934af85fb5a43e69ecb0f5 (diff)
downloadlinux-b7d6c30333239f77f8e51423064a623acc7fd127.tar.xz
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/blk-core.c')
-rw-r--r--block/blk-core.c12
1 files changed, 0 insertions, 12 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 538cbc725620..409e1a6b73b0 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1362,18 +1362,6 @@ void blk_account_io_start(struct request *rq, bool new_io)
part_stat_inc(part, merges[rw]);
} else {
part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
- if (!hd_struct_try_get(part)) {
- /*
- * The partition is already being removed,
- * the request will be accounted on the disk only
- *
- * We take a reference on disk->part0 although that
- * partition will never be deleted, so we can treat
- * it as any other partition.
- */
- part = &rq->rq_disk->part0;
- hd_struct_get(part);
- }
part_inc_in_flight(rq->q, part, rw);
rq->part = part;
}