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Subject[PATCH] perf report: Fix a memory corrupton issue when enabling --branch-history
Date
Following command lines will cause perf crash.

perf record -j call -g -a <application>
perf report --branch-history

*** Error in `perf': double free or corruption (!prev): 0x00000000104aa040 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x77725)[0x7f6b37254725]
/lib/x86_64-linux-gnu/libc.so.6(+0x7ff4a)[0x7f6b3725cf4a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f6b37260abc]
perf[0x51b914]
perf(hist_entry_iter__add+0x1e5)[0x51f305]
perf[0x43cf01]
perf[0x4fa3bf]
perf[0x4fa923]
perf[0x4fd396]
perf[0x4f9614]
perf(perf_session__process_events+0x89e)[0x4fc38e]
perf(cmd_report+0x15d2)[0x43f202]
perf[0x4a059f]
perf(main+0x631)[0x427b71]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7f6b371fd830]
perf(_start+0x29)[0x427d89]

The memory corruption happens at:

iter_add_next_cumulative_entry()
{
...
for (i = 0; i < iter->curr; i++) {
...
}

Whatever in iter_next_cumulative_entry() or in iter_add_next_cumulative_entry(),
they all don't check if iter->curr exceeds the array 'he_cache[]'.

If there are too many nodes in callchain, it's possible that iter->curr >
iter->max_stack, then memory corruption occurs.

This patch will reallocate array 'he_cache[]' in iter_next_cumulative_entry()
if necessary (the case of too many nodes in callchain).

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
---
tools/perf/util/hist.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index b614095..71f07d2 100644
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -926,11 +926,32 @@ iter_next_cumulative_entry(struct hist_entry_iter *iter,
struct addr_location *al)
{
struct callchain_cursor_node *node;
+ struct hist_entry **tmp;
+ int i;

node = callchain_cursor_current(&callchain_cursor);
if (node == NULL)
return 0;

+ /*
+ * If there are too many nodes in callchain,
+ * increase the size of he_cache[].
+ */
+ if (iter->curr == iter->max_stack) {
+ i = 2 * iter->max_stack + 1;
+ tmp = realloc(iter->priv, sizeof(struct hist_entry *) * i);
+ if (tmp == NULL) {
+ /*
+ * No need to free iter->priv here. It will be
+ * freed in iter_finish_cumulative_entry.
+ */
+ return 0;
+ }
+
+ iter->priv = tmp;
+ iter->max_stack = i;
+ }
+
return fill_callchain_info(al, node, iter->hide_unresolved);
}

--
2.7.4
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