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Subject[PATCH 5.4 333/434] perf session: Fix decompression of PERF_RECORD_COMPRESSED records
Date
From: Alexey Budankov <alexey.budankov@linux.intel.com>

[ Upstream commit bb1835a3b86c73aa534ef6430ad40223728dfbc0 ]

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

$ tools/perf/perf report -vv --stdio
decomp (B): 59593 to 262160
decomp (B): 4438 to 16512
decomp (B): 285 to 880
Looking at the vmlinux_path (8 entries long)
Using vmlinux for symbols
decomp (B): 57474 to 261248
prefetch_event: head=0x3fc78 event->header_size=0x28, mmap_size=0x3fc80: fuzzed or compressed perf.data?
decomp (B): 25 to 32
decomp (B): 52 to 120
...

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>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/cf782c34-f3f8-2f9f-d6ab-145cee0d5322@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/session.c | 44 ++++++++++++++++++++++++---------------
1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 061bb4d6a3f5..5c172845fa5a 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1954,8 +1954,8 @@ out_err:
}

static union perf_event *
-fetch_mmaped_event(struct perf_session *session,
- u64 head, size_t mmap_size, char *buf)
+prefetch_event(char *buf, u64 head, size_t mmap_size,
+ bool needs_swap, union perf_event *error)
{
union perf_event *event;

@@ -1967,20 +1967,32 @@ 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:"
+ " fuzzed or compressed perf.data?\n",__func__, head, event->header.size, mmap_size);

- return event;
+ return error;
+}
+
+static union perf_event *
+fetch_mmaped_event(u64 head, size_t mmap_size, char *buf, bool needs_swap)
+{
+ return prefetch_event(buf, head, mmap_size, needs_swap, ERR_PTR(-EINVAL));
+}
+
+static union perf_event *
+fetch_decomp_event(u64 head, size_t mmap_size, char *buf, bool needs_swap)
+{
+ return prefetch_event(buf, head, mmap_size, needs_swap, NULL);
}

static int __perf_session__process_decomp_events(struct perf_session *session)
@@ -1993,10 +2005,8 @@ 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(decomp->head, decomp->size, decomp->data,
+ session->header.needs_swap);

if (!event)
break;
@@ -2096,7 +2106,7 @@ remap:
}

more:
- event = fetch_mmaped_event(session, head, mmap_size, buf);
+ event = fetch_mmaped_event(head, mmap_size, buf, session->header.needs_swap);
if (IS_ERR(event))
return PTR_ERR(event);

--
2.20.1


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