perf evsel: Validate RAW sample before byte swapping

For an opposite-endian RAW sample, __evsel__parse_sample() passes the
input-controlled size to mem_bswap_64() before checking whether the
payload fits in the event. A truncated record can therefore make the helper
read and write past the event boundary.

A crafted perf.data file makes perf report crash with SIGSEGV. ASan
reports the out-of-bounds access. A regression test puts backed data past
the declared end and shows that it is changed before the parser returns
-EFAULT.

Move the bounds checks before mem_bswap_64(). Check the rounded length too,
because the helper accesses complete 64-bit words. Complete records are
handled as before.

Fixes: f9d8adb345d7adbb ("perf evsel: Fix swap for samples with raw data")
Reviewed-by: Ian Rogers <irogers@google.com>
Assisted-by: Symbolic
Signed-off-by: Mark Amirkan <markdamirkan@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>