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97 lines
3.0 KiB
Diff
97 lines
3.0 KiB
Diff
From 12ca6ad2e3a896256f086497a7c7406a547ee373 Mon Sep 17 00:00:00 2001
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From: Peter Zijlstra <peterz@infradead.org>
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Date: Tue, 15 Dec 2015 13:49:05 +0100
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Subject: perf: Fix race in swevent hash
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There's a race on CPU unplug where we free the swevent hash array
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while it can still have events on. This will result in a
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use-after-free which is BAD.
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Simply do not free the hash array on unplug. This leaves the thing
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around and no use-after-free takes place.
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When the last swevent dies, we do a for_each_possible_cpu() iteration
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anyway to clean these up, at which time we'll free it, so no leakage
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will occur.
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Reported-by: Sasha Levin <sasha.levin@oracle.com>
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Tested-by: Sasha Levin <sasha.levin@oracle.com>
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Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
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Cc: Frederic Weisbecker <fweisbec@gmail.com>
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Cc: Jiri Olsa <jolsa@redhat.com>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Stephane Eranian <eranian@google.com>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Cc: Vince Weaver <vincent.weaver@maine.edu>
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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---
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kernel/events/core.c | 20 +-------------------
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1 file changed, 1 insertion(+), 19 deletions(-)
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diff --git a/kernel/events/core.c b/kernel/events/core.c
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index fd7de04..0a791a2 100644
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--- a/kernel/events/core.c
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+++ b/kernel/events/core.c
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@@ -6488,9 +6488,6 @@ struct swevent_htable {
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/* Recursion avoidance in each contexts */
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int recursion[PERF_NR_CONTEXTS];
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-
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- /* Keeps track of cpu being initialized/exited */
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- bool online;
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};
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static DEFINE_PER_CPU(struct swevent_htable, swevent_htable);
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@@ -6748,14 +6745,8 @@ static int perf_swevent_add(struct perf_event *event, int flags)
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hwc->state = !(flags & PERF_EF_START);
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head = find_swevent_head(swhash, event);
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- if (!head) {
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- /*
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- * We can race with cpu hotplug code. Do not
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- * WARN if the cpu just got unplugged.
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- */
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- WARN_ON_ONCE(swhash->online);
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+ if (WARN_ON_ONCE(!head))
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return -EINVAL;
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- }
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hlist_add_head_rcu(&event->hlist_entry, head);
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perf_event_update_userpage(event);
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@@ -6823,7 +6814,6 @@ static int swevent_hlist_get_cpu(struct perf_event *event, int cpu)
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int err = 0;
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mutex_lock(&swhash->hlist_mutex);
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-
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if (!swevent_hlist_deref(swhash) && cpu_online(cpu)) {
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struct swevent_hlist *hlist;
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@@ -9286,7 +9276,6 @@ static void perf_event_init_cpu(int cpu)
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struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
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mutex_lock(&swhash->hlist_mutex);
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- swhash->online = true;
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if (swhash->hlist_refcount > 0) {
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struct swevent_hlist *hlist;
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@@ -9328,14 +9317,7 @@ static void perf_event_exit_cpu_context(int cpu)
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static void perf_event_exit_cpu(int cpu)
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{
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- struct swevent_htable *swhash = &per_cpu(swevent_htable, cpu);
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-
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perf_event_exit_cpu_context(cpu);
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-
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- mutex_lock(&swhash->hlist_mutex);
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- swhash->online = false;
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- swevent_hlist_release(swhash);
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- mutex_unlock(&swhash->hlist_mutex);
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}
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#else
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static inline void perf_event_exit_cpu(int cpu) { }
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--
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cgit v1.1
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