linux-kernel - [PATCH 09/16] perf symbol: avoid segfault in elf

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Date:	Thu,  9 Aug 2012 15:18:34 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Matt Hellsley <matthltc@...ibm.com>,
	David Hansen <dave@...ux.vnet.ibm.com>
Subject: [PATCH 09/16] perf symbol: 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@...ux.vnet.ibm.com>
---
 tools/perf/util/symbol.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 9e31cbb..6afc92d 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -973,6 +973,10 @@ 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;
 
-- 
1.7.11.3

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