path: root/kernel/taskstats.c
diff options
authorVasiliy Kulikov <segoon@openwall.com>2011-06-27 16:18:11 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2011-07-13 05:29:25 +0200
commit68e62de3e747b9ae5e811a77ccece7c425dae830 (patch)
tree59b341aae5d639d42174b354bbfd8fde24cdfdb5 /kernel/taskstats.c
parent06ce414d4a0811a979a82cddc3e429e6bd704c98 (diff)
taskstats: don't allow duplicate entries in listener mode
commit 26c4caea9d697043cc5a458b96411b86d7f6babd upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel/taskstats.c')
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index ea8384d3caa7..b080920409c6 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -293,16 +293,18 @@ ret:
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;
+ s = NULL;
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;
@@ -311,9 +313,16 @@ static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
listeners = &per_cpu(listener_array, cpu);
+ list_for_each_entry_safe(s2, tmp, &listeners->list, list) {
+ if (s2->pid == pid)
+ goto next_cpu;
+ }
list_add(&s->list, &listeners->list);
+ s = NULL;
+ kfree(s);
return 0;