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author | Tejun Heo <tj@kernel.org> | 2013-06-25 22:48:32 +0400 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-07-22 05:21:25 +0400 |
commit | b6891ed4e66b65e5d6bb36964af0d65a08590018 (patch) | |
tree | e076e3ab8dd110873fe714af8e27c2e6d395b617 /virt/kvm | |
parent | 83d0eb79752482bb888fb6d86ceed8971272f8b4 (diff) | |
download | linux-b6891ed4e66b65e5d6bb36964af0d65a08590018.tar.xz |
cgroup: fix RCU accesses to task->cgroups
commit 14611e51a57df10240817d8ada510842faf0ec51 upstream.
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 <tj@kernel.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'virt/kvm')
0 files changed, 0 insertions, 0 deletions