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authorCarlo Nonato <carlo.nonato95@gmail.com>2020-03-06 15:27:31 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-04-02 17:34:15 +0300
commitc074dded84884b2e17e7c0cba378578f28a133ca (patch)
treedb987c835ac9cb0ba050156abeaecfea1bf2ea37
parentccbedf8c1ed38e291259c9a20010f8cb9a3d162f (diff)
downloadlinux-c074dded84884b2e17e7c0cba378578f28a133ca.tar.xz
block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group()
[ Upstream commit 14afc59361976c0ba39e3a9589c3eaa43ebc7e1d ] The bfq_find_set_group() function takes as input a blkcg (which represents a cgroup) and retrieves the corresponding bfq_group, then it updates the bfq internal group hierarchy (see comments inside the function for why this is needed) and finally it returns the bfq_group. In the hierarchy update cycle, the pointer holding the correct bfq_group that has to be returned is mistakenly used to traverse the hierarchy bottom to top, meaning that in each iteration it gets overwritten with the parent of the current group. Since the update cycle stops at root's children (depth = 2), the overwrite becomes a problem only if the blkcg describes a cgroup at a hierarchy level deeper than that (depth > 2). In this case the root's child that happens to be also an ancestor of the correct bfq_group is returned. The main consequence is that processes contained in a cgroup at depth greater than 2 are wrongly placed in the group described above by BFQ. This commits fixes this problem by using a different bfq_group pointer in the update cycle in order to avoid the overwrite of the variable holding the original group reference. Reported-by: Kwon Je Oh <kwonje.oh2@gmail.com> Signed-off-by: Carlo Nonato <carlo.nonato95@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r--block/bfq-cgroup.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index afbbe5750a1f..7d7aee024ece 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -499,12 +499,13 @@ struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
*/
entity = &bfqg->entity;
for_each_entity(entity) {
- bfqg = container_of(entity, struct bfq_group, entity);
- if (bfqg != bfqd->root_group) {
- parent = bfqg_parent(bfqg);
+ struct bfq_group *curr_bfqg = container_of(entity,
+ struct bfq_group, entity);
+ if (curr_bfqg != bfqd->root_group) {
+ parent = bfqg_parent(curr_bfqg);
if (!parent)
parent = bfqd->root_group;
- bfq_group_set_parent(bfqg, parent);
+ bfq_group_set_parent(curr_bfqg, parent);
}
}