[tip:perf/core] perf symbols: Avoid segfault in elf_strptr

[tip-bot for Cody P Schafer]

Commit-ID:  492746546fe380da768c8496213e26aa91b9b3aa
Gitweb:     http://git.kernel.org/tip/492746546fe380da768c8496213e26aa91b9b3aa
Author:     Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 10 Aug 2012 15:22:55 -0700
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 13 Aug 2012 14:25:23 -0300

perf symbols: Avoid segfault in elf_strptr

If we call elf_section_by_name() with a truncated elf image (ie: the
file header indicates that the section headers are placed past the end
of the file), elf_strptr() causes a segfault within libelf.

Avoid this by checking that we can access the section string table
properly.

Should really be fixed in libelf/elfutils.

Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
Cc: David Hansen <dave@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Matt Hellsley <matthltc@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Sukadev Bhattiprolu <sukadev@xxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1344637382-22789-10-git-send-email-cody@xxxxxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/symbol-elf.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index a2e994e..a9a194d 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -129,6 +129,10 @@ static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
 	Elf_Scn *sec = NULL;
 	size_t cnt = 1;
 
+	/* Elf is corrupted/truncated, avoid calling elf_strptr. */
+	if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL))
+		return NULL;
+
 	while ((sec = elf_nextscn(elf, sec)) != NULL) {
 		char *str;
 
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