Messages in this thread | | | Date | Mon, 11 Nov 2019 16:46:12 +0100 | From | Jiri Olsa <> | Subject | Re: [RFC] perf session: Fix compression processing |
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On Mon, Nov 11, 2019 at 06:41:47PM +0300, Alexey Budankov wrote: > On 11.11.2019 17:56, Jiri Olsa wrote: > > On Mon, Nov 11, 2019 at 05:38:49PM +0300, Alexey Budankov wrote: > >> > >> On 04.11.2019 1:24, Jiri Olsa wrote: > >>> hi, > >> <SNIP> > >>> --- > >>> The compressed data processing occasionally fails with: > >>> $ perf report --stdio -vv > >>> decomp (B): 44519 to 163000 > >>> decomp (B): 48119 to 174800 > >>> decomp (B): 65527 to 131072 > >>> fetch_mmaped_event: head=0x1ffe0 event->header_size=0x28, mmap_size=0x20000: fuzzed perf.data? > >>> Error: > >>> failed to process sample > >>> ... > >>> > >>> It's caused by recent fuzzer fix that does not take into account > >>> that compressed data do not need to by fully present in the buffer, > >>> so it's ok to just return NULL and not to fail. > >>> > >>> Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing invalid header.size") > >>> Link: http://lkml.kernel.org/n/tip-q1biqscs4stcmc9bs1iokfro@git.kernel.org > >>> Signed-off-by: Jiri Olsa <jolsa@kernel.org> > >>> --- > >>> tools/perf/util/session.c | 8 +++++--- > >>> 1 file changed, 5 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > >>> index f07b8ecb91bc..3589ed14a629 100644 > >>> --- a/tools/perf/util/session.c > >>> +++ b/tools/perf/util/session.c > >>> @@ -1959,7 +1959,7 @@ static int __perf_session__process_pipe_events(struct perf_session *session) > >>> > >>> static union perf_event * > >>> fetch_mmaped_event(struct perf_session *session, > >>> - u64 head, size_t mmap_size, char *buf) > >>> + u64 head, size_t mmap_size, char *buf, bool decomp) > >> > >> bools in interface make code less transparent. > >> > >>> { > >>> union perf_event *event; > >>> > >>> @@ -1979,6 +1979,8 @@ fetch_mmaped_event(struct perf_session *session, > >>> /* We're not fetching the event so swap back again */ > >>> if (session->header.needs_swap) > >>> perf_event_header__bswap(&event->header); > >>> + if (decomp) > >>> + return NULL; > >>> pr_debug("%s: head=%#" PRIx64 " event->header_size=%#x, mmap_size=%#zx: fuzzed perf.data?\n", > >>> __func__, head, event->header.size, mmap_size); > >>> return ERR_PTR(-EINVAL); > >>> @@ -1997,7 +1999,7 @@ static int __perf_session__process_decomp_events(struct perf_session *session) > >>> return 0; > >>> > >>> while (decomp->head < decomp->size && !session_done()) { > >>> - union perf_event *event = fetch_mmaped_event(session, decomp->head, decomp->size, decomp->data); > >>> + union perf_event *event = fetch_mmaped_event(session, decomp->head, decomp->size, decomp->data, true); > >> > >> It looks like this call can be skipped, at all, in this case. > > > > not sure what you mean, we are in decomp code no? > > Ok, it is inside "not fetching" branch. > NULL return value means to proceed getting further over the trace. > Checking record type == COMPRESSED at the higher level could > probably be cleaner fix and also work faster.
any chance you could post the fix? the patch I did was a quick fix to get the feature working for presentation ;-) you're probably thinking of the proper approach
thanks, jirka
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