lkml.org 
[lkml]   [2019]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH 2/3] Fix annotate.c use of uninitialized value error
From
Our local MSAN (Memory Sanitizer) build of perf throws a warning
that comes from the "dso__disassemble_filename" function in
"tools/perf/util/annotate.c" when running perf record.

The warning stems from the call to readlink, in which "build_id_path"
was being read into "linkname". Since readlink does not null terminate,
an uninitialized memory access would later occur when "linkname" is
passed into the strstr function. This is simply fixed by null-terminating
"linkname" after the call to readlink.

To reproduce this warning, build perf by running:
make -C tools/perf CLANG=1 CC=clang EXTRA_CFLAGS="-fsanitize=memory\
-fsanitize-memory-track-origins"

(Additionally, llvm might have to be installed and clang might have to
be specified as the compiler - export CC=/usr/bin/clang)

then running:
tools/perf/perf record -o - ls / | tools/perf/perf --no-pager annotate\
-i - --stdio

Please see the cover letter for why false positive warnings may be
generated.

Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
---
tools/perf/util/annotate.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 70de8f6b3aee..d8bfb561bc35 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1627,6 +1627,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
char *build_id_filename;
char *build_id_path = NULL;
char *pos;
+ int len;

if (dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS &&
!dso__is_kcore(dso))
@@ -1655,10 +1656,16 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
dirname(build_id_path);

- if (dso__is_kcore(dso) ||
- readlink(build_id_path, linkname, sizeof(linkname)) < 0 ||
- strstr(linkname, DSO__NAME_KALLSYMS) ||
- access(filename, R_OK)) {
+ if (dso__is_kcore(dso))
+ goto fallback;
+
+ len = readlink(build_id_path, linkname, sizeof(linkname));
+ if (len < 0)
+ goto fallback;
+
+ linkname[len] = '\0';
+ if (strstr(linkname, DSO__NAME_KALLSYMS) ||
+ access(filename, R_OK)) {
fallback:
/*
* If we don't have build-ids or the build-id file isn't in the
--
2.22.0.657.g960e92d24f-goog
\
 
 \ /
  Last update: 2019-07-25 01:45    [W:0.131 / U:1.600 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site