File regcomp-double-free.patch of Package glibc.39825
From 6a52d5cab01ee8d3303f7c0939d6b2618c8a9606 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Mon, 21 Jul 2025 21:43:49 +0200
Subject: [PATCH] posix: Fix double-free after allocation failure in regcomp
(bug 33185)
If a memory allocation failure occurs during bracket expression
parsing in regcomp, a double-free error may result.
Reported-by: Anastasia Belova <abelova@astralinux.ru>
Co-authored-by: Paul Eggert <eggert@cs.ucla.edu>
Reviewed-by: Andreas K. Huettel <dilfridge@gentoo.org>
(cherry picked from commit 7ea06e994093fa0bcca0d0ee2c1db271d8d7885d)
---
NEWS | 1 +
posix/Makefile | 1 +
posix/regcomp.c | 4 +-
posix/tst-regcomp-bracket-free.c | 176 +++++++++++++++++++++++++++++++
4 files changed, 181 insertions(+), 1 deletion(-)
create mode 100644 posix/tst-regcomp-bracket-free.c
diff --git a/posix/Makefile b/posix/Makefile
index 3d368b91f6..1fc0f565af 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -305,6 +305,7 @@ tests := \
tst-posix_spawn-setsid \
tst-preadwrite \
tst-preadwrite64 \
+ tst-regcomp-bracket-free \
tst-regcomp-truncated \
tst-regex \
tst-regex2 \
diff --git a/posix/regcomp.c b/posix/regcomp.c
index 12650714c0..dff00b7cab 100644
--- a/posix/regcomp.c
+++ b/posix/regcomp.c
@@ -3384,6 +3384,7 @@ parse_bracket_exp (re_string_t *regexp, re_dfa_t *dfa, re_token_t *token,
{
#ifdef RE_ENABLE_I18N
free_charset (mbcset);
+ mbcset = NULL;
#endif
/* Build a tree for simple bracket. */
br_token.type = SIMPLE_BRACKET;
@@ -3399,7 +3400,8 @@ parse_bracket_exp (re_string_t *regexp, re_dfa_t *dfa, re_token_t *token,
parse_bracket_exp_free_return:
re_free (sbcset);
#ifdef RE_ENABLE_I18N
- free_charset (mbcset);
+ if (__glibc_likely (mbcset != NULL))
+ free_charset (mbcset);
#endif /* RE_ENABLE_I18N */
return NULL;
}
diff --git a/posix/tst-regcomp-bracket-free.c b/posix/tst-regcomp-bracket-free.c
new file mode 100644
index 0000000000..3c091d8c44
--- /dev/null
+++ b/posix/tst-regcomp-bracket-free.c
@@ -0,0 +1,176 @@
+/* Test regcomp bracket parsing with injected allocation failures (bug 33185).
+ Copyright (C) 2025 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This test invokes regcomp multiple times, failing one memory
+ allocation in each call. The function call should fail with
+ REG_ESPACE (or succeed if it can recover from the allocation
+ failure). Previously, there was double-free bug. */
+
+#include <errno.h>
+#include <regex.h>
+#include <stdio.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/support.h>
+
+/* Data structure allocated via MAP_SHARED, so that writes from the
+ subprocess are visible. */
+struct shared_data
+{
+ /* Number of tracked allocations performed so far. */
+ volatile unsigned int allocation_count;
+
+ /* If this number is reached, one allocation fails. */
+ volatile unsigned int failing_allocation;
+
+ /* The subprocess stores the expected name here. */
+ char name[100];
+};
+
+/* Allocation count in shared mapping. */
+static struct shared_data *shared;
+
+/* Returns true if a failure should be injected for this allocation. */
+static bool
+fail_this_allocation (void)
+{
+ if (shared != NULL)
+ {
+ unsigned int count = shared->allocation_count;
+ shared->allocation_count = count + 1;
+ return count == shared->failing_allocation;
+ }
+ else
+ return false;
+}
+
+/* Failure-injecting wrappers for allocation functions used by glibc. */
+
+void *
+malloc (size_t size)
+{
+ if (fail_this_allocation ())
+ {
+ errno = ENOMEM;
+ return NULL;
+ }
+ extern __typeof (malloc) __libc_malloc;
+ return __libc_malloc (size);
+}
+
+void *
+calloc (size_t a, size_t b)
+{
+ if (fail_this_allocation ())
+ {
+ errno = ENOMEM;
+ return NULL;
+ }
+ extern __typeof (calloc) __libc_calloc;
+ return __libc_calloc (a, b);
+}
+
+void *
+realloc (void *ptr, size_t size)
+{
+ if (fail_this_allocation ())
+ {
+ errno = ENOMEM;
+ return NULL;
+ }
+ extern __typeof (realloc) __libc_realloc;
+ return __libc_realloc (ptr, size);
+}
+
+/* No-op subprocess to verify that support_isolate_in_subprocess does
+ not perform any heap allocations. */
+static void
+no_op (void *ignored)
+{
+}
+
+/* Perform a regcomp call in a subprocess. Used to count its
+ allocations. */
+static void
+initialize (void *regexp1)
+{
+ const char *regexp = regexp1;
+
+ shared->allocation_count = 0;
+
+ regex_t reg;
+ TEST_COMPARE (regcomp (®, regexp, 0), 0);
+}
+
+/* Perform regcomp in a subprocess with fault injection. */
+static void
+test_in_subprocess (void *regexp1)
+{
+ const char *regexp = regexp1;
+ unsigned int inject_at = shared->failing_allocation;
+
+ regex_t reg;
+ int ret = regcomp (®, regexp, 0);
+
+ if (ret != 0)
+ {
+ TEST_COMPARE (ret, REG_ESPACE);
+ printf ("info: allocation %u failure results in return value %d,"
+ " error %s (%d)\n",
+ inject_at, ret, strerrorname_np (errno), errno);
+ }
+}
+
+static int
+do_test (void)
+{
+ char regexp[] = "[:alpha:]";
+
+ shared = support_shared_allocate (sizeof (*shared));
+
+ /* Disable fault injection. */
+ shared->failing_allocation = ~0U;
+
+ support_isolate_in_subprocess (no_op, NULL);
+ TEST_COMPARE (shared->allocation_count, 0);
+
+ support_isolate_in_subprocess (initialize, regexp);
+
+ /* The number of allocations in the successful case, plus some
+ slack. Once the number of expected allocations is exceeded,
+ injecting further failures does not make a difference. */
+ unsigned int maximum_allocation_count = shared->allocation_count;
+ printf ("info: successful call performs %u allocations\n",
+ maximum_allocation_count);
+ maximum_allocation_count += 10;
+
+ for (unsigned int inject_at = 0; inject_at <= maximum_allocation_count;
+ ++inject_at)
+ {
+ shared->allocation_count = 0;
+ shared->failing_allocation = inject_at;
+ support_isolate_in_subprocess (test_in_subprocess, regexp);
+ }
+
+ support_shared_free (shared);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
--
2.50.1
