On Mon, Dec 11, 2017 at 12:44 PM, Jeremy Feusi <jer...@feusi.co> wrote:
> Hi,
> I am working on a project for school in which I use afl to find bugs in
> software and I decided to fuzz grep. In doing so I discovered a
> segfault. When using gdb, the location of the segfault varies, which
> puzzles me and so I cannot include any further information.
> The command to obtain this bug is:
> grep -o -E -f <seg-file>
> where <seg-file> is the file attached.
>
> I am using grep 3.1 on arch linux.
> cheers
> Jeremy
Thank you for the report.
This has been an issue since about grep-2.6.1.
It gave a proper diagnostic until 2.5.4:
$ grep-2.5.4/bin/grep -E -f <(printf %080000d 0|tr 0 '(')
grep-2.5.4/bin/grep: Unmatched ( or \(
[Exit 2]
Starting in approximately 2.6.1 (I don't have 2.6.0 handy) it
would fail like this:
$ grep-2.6.1/bin/grep -E -f <(printf %080000d 0|tr 0 '(')
Segmentation fault (core dumped)
Using the latest with -P works fine:
$ grep -P -f <(printf %080000d 0|tr 0 '(')
grep: parentheses are too deeply nested
[Exit 2]
Here's a nearly-complete patch to make grep diagnose the generic
"stack overflow" problem:
From 1751a1abf1ff26d5467e515c8da4dea7053f73c8 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@fb.com>
Date: Tue, 12 Dec 2017 09:05:55 -0800
Subject: [PATCH] grep: diagnose stack overflow rather than segfaulting
* bootstrap.conf (gnulib_modules): Add c-stack.
* src/grep.c: Include "c-stack.h".
(main): Call c_stack_action (NULL);
* tests/stack-overflow: New file.
* tests/Makefile.am (TESTS): Add name of new file.
* NEWS (Improvements): Mention it.
Reported by Jeremy Feusi in https://bugs.gnu.org/29666.
---
NEWS | 4 ++++
bootstrap.conf | 1 +
src/grep.c | 2 ++
tests/Makefile.am | 1 +
tests/stack-overflow | 16 ++++++++++++++++
5 files changed, 24 insertions(+)
create mode 100755 tests/stack-overflow
diff --git a/NEWS b/NEWS
index 51a1529..16c36d3 100644
--- a/NEWS
+++ b/NEWS
@@ -13,6 +13,10 @@ GNU grep NEWS -*- outline
-*-
The --recursive (-r) option no longer fails on MS-Windows.
[bug introduced in grep 2.11]
+** Improvements
+
+ grep now diagnoses stack overflow. Before, it would often simply segfault.
+
* Noteworthy changes in release 3.1 (2017-07-02) [stable]
diff --git a/bootstrap.conf b/bootstrap.conf
index 73f1573..185cd19 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -27,6 +27,7 @@ alloca
announce-gen
argmatch
c-ctype
+c-stack
closeout
dfa
do-release-commit-and-tag
diff --git a/src/grep.c b/src/grep.c
index ad5cfa2..a444cf3 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -30,6 +30,7 @@
#include "argmatch.h"
#include "c-ctype.h"
+#include "c-stack.h"
#include "closeout.h"
#include "colorize.h"
#include "die.h"
@@ -2450,6 +2451,7 @@ main (int argc, char **argv)
init_localeinfo (&localeinfo);
atexit (clean_up_stdout);
+ c_stack_action (NULL);
last_recursive = 0;
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 66fb461..4aca63b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -151,6 +151,7 @@ TESTS = \
skip-read \
spencer1 \
spencer1-locale \
+ stack-overflow \
status \
surrogate-pair \
symlink \
diff --git a/tests/stack-overflow b/tests/stack-overflow
new file mode 100755
index 0000000..2042ebc
--- /dev/null
+++ b/tests/stack-overflow
@@ -0,0 +1,16 @@
+#!/bin/sh
+# Ensure a stack overflow no longer segfaults
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+
+# Too many open parentheses.
+printf %080000d 0|tr 0 '(' > in || framework_failure_
+echo grep: stack overflow > exp || framework_failure_
+
+fail=0
+returns_ 2 grep -E -f in >out 2>err || fail=1
+
+compare /dev/null out || fail=1
+compare exp err || fail=1
+
+Exit $fail
--
2.14.1.729.g59c0ea183
