perf report: Fix memory corruption in --branch-history mode --branch-history

Jin Yao reported memory corrupton in perf report with
branch info used for stack trace:

  > 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]

For the cumulative output, we allocate the he_cache array based on the
--max-stack option value and populate it with data from 'callchain_cursor'.

The --max-stack option value does not ensure now the limit for number of
callchain_cursor nodes, so the cumulative iter code will allocate smaller array
than it's actually needed and cause above corruption.

I think the --max-stack limit does not apply here anyway, because we add
callchain data as normal hist entries, while the --max-stack control the limit
of single entry callchain depth.

Using the callchain_cursor.nr as he_cache array count to fix this. Also
removing struct hist_entry_iter::max_stack, because there's no longer any use
for it.

We need more fixes to ensure that the branch stack code follows properly the
logic of --max-stack, which is not the case at the moment.

Original-patch-by: Jin Yao <yao.jin@linux.intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Reported-by: Jin Yao <yao.jin@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180216123619.GA9945@krava
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/hist.c b/tools/perf/util/hist.c
index b6140950301eec7b41c325fbe75f02bc8f2ecac6..44a8456cea1042b293b82529586e93b77d76869c 100644 (file)
--- a/tools/perf/util/hist.c
+++ b/tools/perf/util/hist.c
@@ -879,7 +879,7 @@ iter_prepare_cumulative_entry(struct hist_entry_iter *iter,
         * cumulated only one time to prevent entries more than 100%
         * overhead.
         */
-       he_cache = malloc(sizeof(*he_cache) * (iter->max_stack + 1));
+       he_cache = malloc(sizeof(*he_cache) * (callchain_cursor.nr + 1));
        if (he_cache == NULL)
                return -ENOMEM;
 
@@ -1045,8 +1045,6 @@ int hist_entry_iter__add(struct hist_entry_iter *iter, struct addr_location *al,
        if (err)
                return err;
 
-       iter->max_stack = max_stack_depth;
-
        err = iter->ops->prepare_entry(iter, al);
        if (err)
                goto out;

diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index 02721b5797464605519967969e0ec78f0038123c..e869cad4d89f1b31fbed8f8359613b094c2382f4 100644 (file)
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -107,7 +107,6 @@ struct hist_entry_iter {
        int curr;
 
        bool hide_unresolved;
-       int max_stack;
 
        struct perf_evsel *evsel;
        struct perf_sample *sample;