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perf buildid: Do not assume that readlink() returns a null terminated string

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Valgrind was complaining:

  $ valgrind ./perf list >/dev/null
  ==11643== Memcheck, a memory error detector
  ==11643== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
  ==11643== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
  ==11643== Command: ./perf list
  ==11643==
  ==11643== Conditional jump or move depends on uninitialised value(s)
  ==11643==    at 0x4C30620: rindex (vg_replace_strmem.c:199)
  ==11643==    by 0x49DAA9: build_id_cache__origname (build-id.c:198)
  ==11643==    by 0x49E1C7: build_id_cache__valid_id (build-id.c:222)
  ==11643==    by 0x49E1C7: build_id_cache__list_all (build-id.c:507)
  ==11643==    by 0x4B9C8F: print_sdt_events (parse-events.c:2067)
  ==11643==    by 0x4BB0B3: print_events (parse-events.c:2313)
  ==11643==    by 0x439501: cmd_list (builtin-list.c:53)
  ==11643==    by 0x497150: run_builtin (perf.c:359)
  ==11643==    by 0x428CE0: handle_internal_command (perf.c:421)
  ==11643==    by 0x428CE0: run_argv (perf.c:467)
  ==11643==    by 0x428CE0: main (perf.c:614)
  [...]

Additionally, a zero length result from readlink() is not very interesting.

Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170322130624.21881-3-tommi.t.rantala@nokia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Tommi Rantala 2017-03-22 15:06:20 +02:00 committed by Arnaldo Carvalho de Melo
parent 2ccc220238
commit 5a2342111c
1 changed files with 5 additions and 1 deletions
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6
tools/perf/util/build-id.c
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@ -182,13 +182,17 @@ char *build_id_cache__origname(const char *sbuild_id)
char buf[PATH_MAX];
char *ret = NULL, *p;
size_t offs = 5; /* == strlen("../..") */
ssize_t len;
linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
if (!linkname)
return NULL;
if (readlink(linkname, buf, PATH_MAX) < 0)
len = readlink(linkname, buf, sizeof(buf) - 1);
if (len <= 0)
goto out;
buf[len] = '\0';
/* The link should be "../..<origpath>/<sbuild_id>" */
p = strrchr(buf, '/'); /* Cut off the "/<sbuild_id>" */
if (p && (p > buf + offs)) {