Commit 3ac1707a authored Mar 12, 2013 by Li Zefan Committed by Tejun Heo Mar 20, 2013

cgroup: fix an off-by-one bug which may trigger BUG_ON()



The 3rd parameter of flex_array_prealloc() is the number of elements,
not the index of the last element.

The effect of the bug is, when opening cgroup.procs, a flex array will
be allocated and all elements of the array is allocated with
GFP_KERNEL flag, but the last one is GFP_ATOMIC, and if we fail to
allocate memory for it, it'll trigger a BUG_ON().

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org

parent 80f36c2a

kernel/cgroup.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2076,7 +2076,7 @@ static int cgroup_attach_proc(struct cgroup cgrp, struct task_struct leader)
		if (!group)
		return -ENOMEM;
		/* pre-allocate to guarantee space while iterating in rcu read-side. */
		retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
		retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
		if (retval)
		goto out_free_group_list;