commit: 26c4caea9d697043cc5a458b96411b86d7f6babd
From: Vasiliy Kulikov <seg...@openwall.com>
Date: Mon, 27 Jun 2011 16:18:11 -0700
Subject: [PATCH] taskstats: don't allow duplicate entries in listener mode
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 <sego...@gmail.com>
Cc: Balbir Singh <bsinghar...@gmail.com>
Cc: <sta...@kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
---
kernel/taskstats.c | 15 ++++++++++++---
1 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index 9ffea36..fc0f220 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -285,16 +285,18 @@ 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;
@@ -303,9 +305,16 @@ static int add_del_listener(pid_t pid, const struct
cpumask *mask, int isadd)
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);
+ s = NULL;
+next_cpu:
up_write(&listeners->sem);
}
+ kfree(s);
return 0;
}
_______________________________________________
stable mailing list
stable@linux.kernel.org
http://linux.kernel.org/mailman/listinfo/stable
