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Subject[PATCH v1] perf session: fix decompression of PERF_RECORD_COMPRESSED records
Date

Avoid termination of trace loading in case the last record in
the decompressed buffer partly resides in the following
mmaped PERF_RECORD_COMPRESSED record. In this case NULL value
returned by fetch_mmaped_event() means to proceed to the next
mmaped record then decompress it and load compressed events.

The issue can be reproduced like this:

$ perf record -z -- some_long_running_workload
$ 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
...

Testing:
71: Zstd perf.data compression/decompression : Ok

Fixes: 57fc032ad643 ("perf session: Avoid infinite loop when seeing invalid header.size")
Link: https://marc.info/?l=linux-kernel&m=156580812427554&w=2
Co-developed-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
tools/perf/util/session.c | 47 +++++++++++++++++++++++++++++++++--------------
1 file changed, 33 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index f07b8ecb91bc..3f6f812ec4ed 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1957,9 +1957,31 @@ static int __perf_session__process_pipe_events(struct perf_session *session)
return err;
}

+static union perf_event *
+prefetch_event(char *buf, u64 head, size_t mmap_size,
+ bool needs_swap, union perf_event *ret);
+
static union perf_event *
fetch_mmaped_event(struct perf_session *session,
u64 head, size_t mmap_size, char *buf)
+{
+ return prefetch_event(buf, head, mmap_size,
+ session->header.needs_swap,
+ ERR_PTR(-EINVAL));
+}
+
+static union perf_event *
+fetch_decomp_event(struct perf_session *session,
+ u64 head, size_t mmap_size, char *buf)
+{
+ return prefetch_event(buf, head, mmap_size,
+ session->header.needs_swap,
+ NULL);
+}
+
+static union perf_event *
+prefetch_event(char *buf, u64 head, size_t mmap_size,
+ bool needs_swap, union perf_event *ret)
{
union perf_event *event;

@@ -1971,20 +1993,20 @@ fetch_mmaped_event(struct perf_session *session,
return NULL;

event = (union perf_event *)(buf + head);
+ if (needs_swap)
+ perf_event_header__bswap(&event->header);

- if (session->header.needs_swap)
+ if (head + event->header.size <= mmap_size)
+ return event;
+
+ /* We're not fetching the event so swap back again */
+ if (needs_swap)
perf_event_header__bswap(&event->header);

- if (head + event->header.size > mmap_size) {
- /* We're not fetching the event so swap back again */
- if (session->header.needs_swap)
- perf_event_header__bswap(&event->header);
- 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);
- }
+ pr_debug("%s: head=%#" PRIx64 " event->header_size=%#x, mmap_size=%#zx\n",
+ __func__, head, event->header.size, mmap_size);

- return event;
+ return ret;
}

static int __perf_session__process_decomp_events(struct perf_session *session)
@@ -1997,10 +2019,7 @@ 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);
-
- if (IS_ERR(event))
- return PTR_ERR(event);
+ union perf_event *event = fetch_decomp_event(session, decomp->head, decomp->size, decomp->data);

if (!event)
break;
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