If we are doing a self-checkpoint, we will not be frozen and the get_freezer_task() will return NULL. If we have children, then may_checkpoint_task() will attempt to make sure that they are in the same cgroup as the freezer task, which will attempt to lock a NULL task pointer (and thus go boom).
This patch just inserts a check before in_same_cgroup_freezer() call to make sure we have a freezer task. The existing check is aimed to determine if a task is not frozen alongside the root, so this addition catches the case where it is impossible. Signed-off-by: Dan Smith <[email protected]> --- kernel/checkpoint/checkpoint.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/checkpoint/checkpoint.c b/kernel/checkpoint/checkpoint.c index 0f46acf..33f53e9 100644 --- a/kernel/checkpoint/checkpoint.c +++ b/kernel/checkpoint/checkpoint.c @@ -262,8 +262,12 @@ static int may_checkpoint_task(struct ckpt_ctx *ctx, struct task_struct *t) if (t->exit_state) return 0; - /* verify that all tasks belongs to same freezer cgroup */ - if (t != current && !in_same_cgroup_freezer(t, ctx->root_freezer)) { + /* + * verify that we have a freezer cgroup and that all tasks + * belong to the same one + */ + if (t != current && (!ctx->root_freezer || + !in_same_cgroup_freezer(t, ctx->root_freezer))) { _ckpt_err(ctx, -EBUSY, "%(T)Not frozen or wrong cgroup\n"); return -EBUSY; } -- 1.7.2.2 _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
