82 lines
2.6 KiB
Diff
82 lines
2.6 KiB
Diff
From: Vasiliy Kulikov <segoon@openwall.com>
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Date: Mon, 27 Jun 2011 16:18:11 -0700
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Subject: [PATCH] taskstats: don't allow duplicate entries in listener mode
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commit 26c4caea9d697043cc5a458b96411b86d7f6babd upstream.
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Currently a single process may register exit handlers unlimited times.
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It may lead to a bloated listeners chain and very slow process
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terminations.
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Eg after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
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kernel memory is stolen for the handlers chain and "time id" shows 2-7
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seconds instead of normal 0.003. It makes it possible to exhaust all
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kernel memory and to eat much of CPU time by triggerring numerous exits
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on a single CPU.
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The patch limits the number of times a single process may register
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itself on a single CPU to one.
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One little issue is kept unfixed - as taskstats_exit() is called before
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exit_files() in do_exit(), the orphaned listener entry (if it was not
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explicitly deregistered) is kept until the next someone's exit() and
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implicit deregistration in send_cpu_listeners(). So, if a process
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registered itself as a listener exits and the next spawned process gets
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the same pid, it would inherit taskstats attributes.
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Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
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Cc: Balbir Singh <bsingharora@gmail.com>
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Cc: <stable@kernel.org>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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kernel/taskstats.c | 15 ++++++++++++---
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1 files changed, 12 insertions(+), 3 deletions(-)
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diff --git a/kernel/taskstats.c b/kernel/taskstats.c
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index 9ffea36..fc0f220 100644
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--- a/kernel/taskstats.c
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+++ b/kernel/taskstats.c
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@@ -285,16 +285,18 @@ ret:
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static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
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{
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struct listener_list *listeners;
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- struct listener *s, *tmp;
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+ struct listener *s, *tmp, *s2;
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unsigned int cpu;
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if (!cpumask_subset(mask, cpu_possible_mask))
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return -EINVAL;
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+ s = NULL;
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if (isadd == REGISTER) {
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for_each_cpu(cpu, mask) {
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- s = kmalloc_node(sizeof(struct listener), GFP_KERNEL,
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- cpu_to_node(cpu));
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+ if (!s)
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+ s = kmalloc_node(sizeof(struct listener),
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+ GFP_KERNEL, cpu_to_node(cpu));
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if (!s)
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goto cleanup;
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s->pid = pid;
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@@ -303,9 +305,16 @@ static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
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listeners = &per_cpu(listener_array, cpu);
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down_write(&listeners->sem);
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+ list_for_each_entry_safe(s2, tmp, &listeners->list, list) {
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+ if (s2->pid == pid)
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+ goto next_cpu;
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+ }
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list_add(&s->list, &listeners->list);
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+ s = NULL;
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+next_cpu:
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up_write(&listeners->sem);
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}
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+ kfree(s);
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return 0;
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}
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--
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1.7.5.4
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