From: Tejun Heo Date: Tue, 25 Jun 2013 18:48:32 +0000 (-0700) Subject: cgroup: fix RCU accesses to task->cgroups X-Git-Tag: omap-for-v3.11/fixes-for-merge-window~44^2~5 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=14611e51a57df10240817d8ada510842faf0ec51;p=pandora-kernel.git cgroup: fix RCU accesses to task->cgroups task->cgroups is a RCU pointer pointing to struct css_set. A task switches to a different css_set on cgroup migration but a css_set doesn't change once created and its pointers to cgroup_subsys_states aren't RCU protected. task_subsys_state[_check]() is the macro to acquire css given a task and subsys_id pair. It RCU-dereferences task->cgroups->subsys[] not task->cgroups, so the RCU pointer task->cgroups ends up being dereferenced without read_barrier_depends() after it. It's broken. Fix it by introducing task_css_set[_check]() which does RCU-dereference on task->cgroups. task_subsys_state[_check]() is reimplemented to directly dereference ->subsys[] of the css_set returned from task_css_set[_check](). This removes some of sparse RCU warnings in cgroup. v2: Fixed unbalanced parenthsis and there's no need to use rcu_dereference_raw() when !CONFIG_PROVE_RCU. Both spotted by Li. Signed-off-by: Tejun Heo Reported-by: Fengguang Wu Acked-by: Li Zefan Cc: stable@vger.kernel.org --- Reading git-diff-tree failed