[PATCH 09/15] perf/ring_buffer: convert ring_buffer.aux_refcount to refcount_t
From: Elena Reshetova <elena.reshetova@intel.com>
Date: 2017-10-20 12:15:51
Also in:
linux-fsdevel, lkml
Subsystem:
performance events subsystem, the rest · Maintainers:
Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds
atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable ring_buffer.aux_refcount is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook <redacted> Reviewed-by: David Windsor <redacted> Reviewed-by: Hans Liljestrand <redacted> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> --- kernel/events/core.c | 2 +- kernel/events/internal.h | 2 +- kernel/events/ring_buffer.c | 6 +++--- 3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 66d7e18..3848480 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c@@ -5182,7 +5182,7 @@ static void perf_mmap_close(struct vm_area_struct *vma) /* this has to be the last one */ rb_free_aux(rb); - WARN_ON_ONCE(atomic_read(&rb->aux_refcount)); + WARN_ON_ONCE(refcount_read(&rb->aux_refcount)); mutex_unlock(&event->mmap_mutex); }
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 1cdd9fa..cc5b545 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h@@ -48,7 +48,7 @@ struct ring_buffer { atomic_t aux_mmap_count; unsigned long aux_mmap_locked; void (*free_aux)(void *); - atomic_t aux_refcount; + refcount_t aux_refcount; void **aux_pages; void *aux_priv;
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 86e1379..08838cd6 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c@@ -357,7 +357,7 @@ void *perf_aux_output_begin(struct perf_output_handle *handle, if (!atomic_read(&rb->aux_mmap_count)) goto err; - if (!atomic_inc_not_zero(&rb->aux_refcount)) + if (!refcount_inc_not_zero(&rb->aux_refcount)) goto err; /*
@@ -655,7 +655,7 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, * we keep a refcount here to make sure either of the two can * reference them safely. */ - atomic_set(&rb->aux_refcount, 1); + refcount_set(&rb->aux_refcount, 1); rb->aux_overwrite = overwrite; rb->aux_watermark = watermark;
@@ -674,7 +674,7 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, void rb_free_aux(struct ring_buffer *rb) { - if (atomic_dec_and_test(&rb->aux_refcount)) + if (refcount_dec_and_test(&rb->aux_refcount)) __rb_free_aux(rb); }
--
2.7.4
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