perf tools: Fix crash in build_id_cache__kallsyms_path()

build_id_cache__kallsyms_path() accepts a string buffer but also allocs
a buffer using asnprintf. Unfortunately, the its only user passes it a
stack-allocated buffer. Freeing it causes crashes like this:

  $ perf script
  *** Error in `/home/wangnan/perf': free(): invalid pointer: 0x00007fffffff9630 ***
  ======= Backtrace: =========
  lib64/libc.so.6(+0x6eeef)[0x7ffff5dbaeef]
  lib64/libc.so.6(+0x78cae)[0x7ffff5dc4cae]
  lib64/libc.so.6(+0x79987)[0x7ffff5dc5987]
  /home/w00229757/perf(build_id_cache__kallsyms_path+0x6b)[0x49681b]
  /home/w00229757/perf[0x4bdd40]
  /home/w00229757/perf(dso__load+0xa3a)[0x4c048a]
  /home/w00229757/perf(map__load+0x6f)[0x4d561f]
  /home/w00229757/perf(thread__find_addr_map+0x235)[0x49e935]
  /home/w00229757/perf(machine__resolve+0x7d)[0x49ec6d]
  /home/w00229757/perf[0x4555a8]
  /home/w00229757/perf[0x4d9507]
  /home/w00229757/perf[0x4d9e80]
  /home/w00229757/perf(ordered_events__flush+0x354)[0x4dd444]
  /home/w00229757/perf(perf_session__process_events+0x3d0)[0x4dc140]
  /home/w00229757/perf(cmd_script+0x12b0)[0x4592e0]
  /home/w00229757/perf[0x4911f1]
  /home/w00229757/perf(main+0x68f)[0x4352ef]
  /lib64/libc.so.6(__libc_start_main+0xf5)[0x7ffff5d6dbd5]
  /home/w00229757/perf[0x435415]
  ======= Memory map: ========

This patch simplifies build_id_cache__kallsyms_path(), not even
considering allocating a string buffer, so never frees anything. Its
caller should manage memory allocation.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Fixes: 01412261d994 ("perf buildid-cache: Use path/to/bin/buildid/elf instead of path/to/bin/buildid")
Link: http://lkml.kernel.org/r/1465271678-7392-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 67f986c..20aef90 100644 (file)
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -147,20 +147,17 @@ static int asnprintf(char **strp, size_t size, const char *fmt, ...)
 char *build_id_cache__kallsyms_path(const char *sbuild_id, char *bf,
                                    size_t size)
 {
-       bool is_alloc = !!bf;
        bool retry_old = true;
 
-       asnprintf(&bf, size, "%s/%s/%s/kallsyms",
-                 buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
+       snprintf(bf, size, "%s/%s/%s/kallsyms",
+                buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
 retry:
        if (!access(bf, F_OK))
                return bf;
-       if (is_alloc)
-               free(bf);
        if (retry_old) {
                /* Try old style kallsyms cache */
-               asnprintf(&bf, size, "%s/%s/%s",
-                         buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
+               snprintf(bf, size, "%s/%s/%s",
+                        buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
                retry_old = false;
                goto retry;
        }