Currently a single process may register exit handlers unlimited times.
It may lead to a bloated listeners chain and very slow process
terminations.
Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
kernel memory is stolen for the handlers chain and "time id" shows 2-7
seconds instead of normal 0.003. It makes it possible to exhaust all
kernel memory and to eat much of CPU time by triggerring numerous exits
on a single CPU.
The patch limits the number of times a single process may register
itself on a single CPU to one.
One little issue is kept unfixed - as taskstats_exit() is called before
exit_files() in do_exit(), the orphaned listener entry (if it was not
explicitly deregistered) is kept until the next someone's exit() and
implicit deregistration in send_cpu_listeners(). So, if a process
registered itself as a listener exits and the next spawned process gets
the same pid, it would inherit taskstats attributes.
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit
26c4caea9d697043cc5a458b96411b86d7f6babd)
CVE-2011-2484
BugLink: http://bugs.launchpad.net/bugs/806390
Signed-off-by: Andy Whitcroft <apw@canonical.com>
static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
{
struct listener_list *listeners;
static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
{
struct listener_list *listeners;
- struct listener *s, *tmp;
+ struct listener *s, *tmp, *s2;
unsigned int cpu;
if (!cpumask_subset(mask, cpu_possible_mask))
return -EINVAL;
unsigned int cpu;
if (!cpumask_subset(mask, cpu_possible_mask))
return -EINVAL;
if (isadd == REGISTER) {
for_each_cpu(cpu, mask) {
if (isadd == REGISTER) {
for_each_cpu(cpu, mask) {
- s = kmalloc_node(sizeof(struct listener), GFP_KERNEL,
- cpu_to_node(cpu));
+ if (!s)
+ s = kmalloc_node(sizeof(struct listener),
+ GFP_KERNEL, cpu_to_node(cpu));
if (!s)
goto cleanup;
s->pid = pid;
if (!s)
goto cleanup;
s->pid = pid;
listeners = &per_cpu(listener_array, cpu);
down_write(&listeners->sem);
listeners = &per_cpu(listener_array, cpu);
down_write(&listeners->sem);
+ list_for_each_entry_safe(s2, tmp, &listeners->list, list) {
+ if (s2->pid == pid)
+ goto next_cpu;
+ }
list_add(&s->list, &listeners->list);
list_add(&s->list, &listeners->list);
up_write(&listeners->sem);
}
up_write(&listeners->sem);
}