[PATCH] perf tools: Fix a problem when opening old perf.data with different byte order

[Wang Nan]

Following error occurs when trying to use 'perf report' on x86_64 to
cross analysis a perf.data generated by an old perf on a big-endian
machine:

 # perf report
 *** Error in `/home/w00229757/perf': free(): invalid next size (fast): 0x00000000032c99f0 ***
 ======= Backtrace: =========
 /lib64/libc.so.6(+0x6eeef)[0x7ff6ff7e2eef]
 /lib64/libc.so.6(+0x78cae)[0x7ff6ff7eccae]
 /lib64/libc.so.6(+0x79987)[0x7ff6ff7ed987]
 /path/to/perf[0x4ac734]
 /path/to/perf[0x4ac829]
 /path/to/perf(perf_header__process_sections+0x129)[0x4ad2c9]
 /path/to/perf(perf_session__read_header+0x2e1)[0x4ad9e1]
 /path/to/perf(perf_session__new+0x168)[0x4bd458]
 /path/to/perf(cmd_report+0xfa0)[0x43eb70]
 /path/to/perf[0x47adc3]
 /path/to/perf(main+0x5f6)[0x42fd06]
 /lib64/libc.so.6(__libc_start_main+0xf5)[0x7ff6ff795bd5]
 /path/to/perf[0x42fe35]
 ======= Memory map: ========
 [SNIP]

The bug is in perf_event__attr_swap(). It swaps all fields in
'struct perf_event_attr' without checking whether the swapped field
exist or not. In addition, in read_event_desc() allocs memory for attr
according to size read from perf.data. Therefore, if the perf.data is
collected by an old perf (without aux_watermark, for example),
when perf_event__attr_swap() swaping attr->aux_watermark it destroy
malloc's metadata.

This patch introduces boundary checking in perf_event__attr_swap(). It
adds macros bswap_field_64 and bswap_field_32 into
perf_event__attr_swap() to make it only swap exist fields.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/perf/util/session.c | 40 ++++++++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 88d87bf..d51ba31 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -517,20 +517,32 @@ void perf_event__attr_swap(struct perf_event_attr *attr)
 {
 	attr->type		= bswap_32(attr->type);
 	attr->size		= bswap_32(attr->size);
-	attr->config		= bswap_64(attr->config);
-	attr->sample_period	= bswap_64(attr->sample_period);
-	attr->sample_type	= bswap_64(attr->sample_type);
-	attr->read_format	= bswap_64(attr->read_format);
-	attr->wakeup_events	= bswap_32(attr->wakeup_events);
-	attr->bp_type		= bswap_32(attr->bp_type);
-	attr->bp_addr		= bswap_64(attr->bp_addr);
-	attr->bp_len		= bswap_64(attr->bp_len);
-	attr->branch_sample_type = bswap_64(attr->branch_sample_type);
-	attr->sample_regs_user	 = bswap_64(attr->sample_regs_user);
-	attr->sample_stack_user  = bswap_32(attr->sample_stack_user);
-	attr->aux_watermark	 = bswap_32(attr->aux_watermark);
-
-	swap_bitfield((u8 *) (&attr->read_format + 1), sizeof(u64));
+#define bswap_safe(f) \
+	(attr->size > offsetof(struct perf_event_attr, f))
+#define bswap_field(f, sz) 			\
+do { 						\
+	if (bswap_safe(f))			\
+		attr->f = bswap_##sz(attr->f);	\
+} while(0)
+#define bswap_field_32(f) bswap_field(f, 32)
+#define bswap_field_64(f) bswap_field(f, 64)
+
+	bswap_field_64(config);
+	bswap_field_64(sample_period);
+	bswap_field_64(sample_type);
+	bswap_field_64(read_format);
+	bswap_field_32(wakeup_events);
+	bswap_field_32(bp_type);
+	bswap_field_64(bp_addr);
+	bswap_field_64(bp_len);
+	bswap_field_64(branch_sample_type);
+	bswap_field_64(sample_regs_user);
+	bswap_field_32(sample_stack_user);
+	bswap_field_32(aux_watermark);
+
+	if (bswap_safe(read_format))
+		swap_bitfield((u8 *) (&attr->read_format + 1),
+			      sizeof(u64));
 }
 
 static void perf_event__hdr_attr_swap(union perf_event *event,
-- 
1.8.3.4

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