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authorPeter Zijlstra <peterz@infradead.org>2013-05-28 10:55:48 +0200
committerIngo Molnar <mingo@kernel.org>2013-05-28 11:05:08 +0200
commit26cb63ad11e04047a64309362674bcbbd6a6f246 (patch)
tree559c0a9778e7aa6639a24d9a7951879dc65d0551 /kernel/events
parent7b959fc582741227a1c4cba710d6aff8fb183128 (diff)
downloadvexpress-lsk-26cb63ad11e04047a64309362674bcbbd6a6f246.tar.gz
perf: Fix perf mmap bugs
Vince reported a problem found by his perf specific trinity fuzzer. Al noticed 2 problems with perf's mmap(): - it has issues against fork() since we use vma->vm_mm for accounting. - it has an rb refcount leak on double mmap(). We fix the issues against fork() by using VM_DONTCOPY; I don't think there's code out there that uses this; we didn't hear about weird accounting problems/crashes. If we do need this to work, the previously proposed VM_PINNED could make this work. Aside from the rb reference leak spotted by Al, Vince's example prog was indeed doing a double mmap() through the use of perf_event_set_output(). This exposes another problem, since we now have 2 events with one buffer, the accounting gets screwy because we account per event. Fix this by making the buffer responsible for its own accounting. Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Link: http://lkml.kernel.org/r/20130528085548.GA12193@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c37
-rw-r--r--kernel/events/internal.h3
2 files changed, 23 insertions, 17 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9dc297faf7c..ae752cd4a08 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2917,7 +2917,7 @@ static void free_event_rcu(struct rcu_head *head)
kfree(event);
}
-static void ring_buffer_put(struct ring_buffer *rb);
+static bool ring_buffer_put(struct ring_buffer *rb);
static void free_event(struct perf_event *event)
{
@@ -3582,13 +3582,13 @@ static struct ring_buffer *ring_buffer_get(struct perf_event *event)
return rb;
}
-static void ring_buffer_put(struct ring_buffer *rb)
+static bool ring_buffer_put(struct ring_buffer *rb)
{
struct perf_event *event, *n;
unsigned long flags;
if (!atomic_dec_and_test(&rb->refcount))
- return;
+ return false;
spin_lock_irqsave(&rb->event_lock, flags);
list_for_each_entry_safe(event, n, &rb->event_list, rb_entry) {
@@ -3598,6 +3598,7 @@ static void ring_buffer_put(struct ring_buffer *rb)
spin_unlock_irqrestore(&rb->event_lock, flags);
call_rcu(&rb->rcu_head, rb_free_rcu);
+ return true;
}
static void perf_mmap_open(struct vm_area_struct *vma)
@@ -3612,18 +3613,20 @@ static void perf_mmap_close(struct vm_area_struct *vma)
struct perf_event *event = vma->vm_file->private_data;
if (atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) {
- unsigned long size = perf_data_size(event->rb);
- struct user_struct *user = event->mmap_user;
struct ring_buffer *rb = event->rb;
+ struct user_struct *mmap_user = rb->mmap_user;
+ int mmap_locked = rb->mmap_locked;
+ unsigned long size = perf_data_size(rb);
- atomic_long_sub((size >> PAGE_SHIFT) + 1, &user->locked_vm);
- vma->vm_mm->pinned_vm -= event->mmap_locked;
rcu_assign_pointer(event->rb, NULL);
ring_buffer_detach(event, rb);
mutex_unlock(&event->mmap_mutex);
- ring_buffer_put(rb);
- free_uid(user);
+ if (ring_buffer_put(rb)) {
+ atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm);
+ vma->vm_mm->pinned_vm -= mmap_locked;
+ free_uid(mmap_user);
+ }
}
}
@@ -3676,9 +3679,7 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
WARN_ON_ONCE(event->ctx->parent_ctx);
mutex_lock(&event->mmap_mutex);
if (event->rb) {
- if (event->rb->nr_pages == nr_pages)
- atomic_inc(&event->rb->refcount);
- else
+ if (event->rb->nr_pages != nr_pages)
ret = -EINVAL;
goto unlock;
}
@@ -3720,12 +3721,14 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
ret = -ENOMEM;
goto unlock;
}
- rcu_assign_pointer(event->rb, rb);
+
+ rb->mmap_locked = extra;
+ rb->mmap_user = get_current_user();
atomic_long_add(user_extra, &user->locked_vm);
- event->mmap_locked = extra;
- event->mmap_user = get_current_user();
- vma->vm_mm->pinned_vm += event->mmap_locked;
+ vma->vm_mm->pinned_vm += extra;
+
+ rcu_assign_pointer(event->rb, rb);
perf_event_update_userpage(event);
@@ -3734,7 +3737,7 @@ unlock:
atomic_inc(&event->mmap_count);
mutex_unlock(&event->mmap_mutex);
- vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+ vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP;
vma->vm_ops = &perf_mmap_vmops;
return ret;
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index eb675c4d59d..5bc6c8e9b85 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -31,6 +31,9 @@ struct ring_buffer {
spinlock_t event_lock;
struct list_head event_list;
+ int mmap_locked;
+ struct user_struct *mmap_user;
+
struct perf_event_mmap_page *user_page;
void *data_pages[0];
};