Messages in this thread Patch in this message | | | Date | Thu, 6 Sep 2018 15:28:59 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCHv3] perf tools: Add struct ordered_events_buffer layer |
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On Mon, Sep 03, 2018 at 07:37:56PM -0700, Stephane Eranian wrote:
SNIP
> > I think the code is correct now for the issue related to uninitialized pointer. > But there is still one problem I found stressing the code with max_alloc_size. > The way the following is written: > > if (!list_empty(cache)) { > new = list_entry(cache->next, struct ordered_event, list); > list_del(&new->list); > } else if (oe->buffer) { > new = oe->buffer + oe->buffer_idx; > if (++oe->buffer_idx == MAX_SAMPLE_BUFFER) > oe->buffer = NULL; > } else if (oe->cur_alloc_size < oe->max_alloc_size) { > size_t size = sizeof(*oe->buffer) MAX_SAMPLE_BUFFER * > sizeof(*new); > > oe->buffer = malloc(size); > if (!oe->buffer) { > free_dup_event(oe, new_event); > return NULL; > } > > pr("alloc size %" PRIu64 "B (+%zu), max %" PRIu64 "B\n", > oe->cur_alloc_size, size, oe->max_alloc_size); > > oe->cur_alloc_size += size; > > You can end up with oe->cur_alloc_size > oe->max_alloc_size in case > the max limit is > really low (< size_t size = sizeof (*oe->buffer) + MAX_SAMPLE_BUFFER * > sizeof(*new); > So I think to make sure you can never allocate more than the max, you > have to do: > > size_t size = sizeof(*oe->buffer) MAX_SAMPLE_BUFFER * sizeof(*new); > if (!list_empty(cache)) { > new = list_entry(cache->next, struct ordered_event, list); > list_del(&new->list); > } else if (oe->buffer) { > new = oe->buffer + oe->buffer_idx; > if (++oe->buffer_idx == MAX_SAMPLE_BUFFER) > oe->buffer = NULL; > } else if ((oe->cur_alloc_size + size) < oe->max_alloc_size) { > > Then you will never allocate more than the max. > I think with this change, we are okay. > Tested-by: Stephane Eranian <eranian@google.com>
yep, makes sense.. something like below then I'll post it on top of the previous patch
thanks, jirka
--- diff --git a/tools/perf/util/ordered-events.c b/tools/perf/util/ordered-events.c index 87171e8fd70d..2d1d0f3c8f77 100644 --- a/tools/perf/util/ordered-events.c +++ b/tools/perf/util/ordered-events.c @@ -101,6 +101,7 @@ static struct ordered_event *alloc_event(struct ordered_events *oe, struct list_head *cache = &oe->cache; struct ordered_event *new = NULL; union perf_event *new_event; + size_t size; new_event = dup_event(oe, event); if (!new_event) @@ -133,6 +134,8 @@ static struct ordered_event *alloc_event(struct ordered_events *oe, * Removal of ordered event object moves it from events to * the cache list. */ + size = sizeof(*oe->buffer) + MAX_SAMPLE_BUFFER * sizeof(*new); + if (!list_empty(cache)) { new = list_entry(cache->next, struct ordered_event, list); list_del(&new->list); @@ -140,10 +143,7 @@ static struct ordered_event *alloc_event(struct ordered_events *oe, new = &oe->buffer->event[oe->buffer_idx]; if (++oe->buffer_idx == MAX_SAMPLE_BUFFER) oe->buffer = NULL; - } else if (oe->cur_alloc_size < oe->max_alloc_size) { - size_t size = sizeof(*oe->buffer) + - MAX_SAMPLE_BUFFER * sizeof(*new); - + } else if ((oe->cur_alloc_size + size) < oe->max_alloc_size) { oe->buffer = malloc(size); if (!oe->buffer) { free_dup_event(oe, new_event);
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