From: Joe Simmons-Talbott <josimmon@redhat.com>
To: libc-alpha@sourceware.org
Cc: Joe Simmons-Talbott <josimmon@redhat.com>
Subject: [PATCH v2] group_member: Get rid of unbounded alloca.
Date: Tue, 8 Aug 2023 14:28:25 -0400 [thread overview]
Message-ID: <20230808182843.678120-1-josimmon@redhat.com> (raw)
Replace a large alloca call with a scratch_buffer to avoid potential stack
overflow. Because group_member doesn't return an error indicator abort if
we are unable to allocate memory. Add a testcase.
Checked on x86_64-linux-gnu.
---
Changes to v1:
* Update commit message and fix typo.
posix/Makefile | 1 +
posix/group_member.c | 27 +++++++++++++++-----------
posix/tst-group_member.c | 41 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 58 insertions(+), 11 deletions(-)
create mode 100644 posix/tst-group_member.c
diff --git a/posix/Makefile b/posix/Makefile
index 3d368b91f6..7491ee8917 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -293,6 +293,7 @@ tests := \
tst-glob_symlinks \
tst-gnuglob \
tst-gnuglob64 \
+ tst-group_member \
tst-mmap \
tst-mmap-offset \
tst-nanosleep \
diff --git a/posix/group_member.c b/posix/group_member.c
index 22422b1f9f..42a4adb9b4 100644
--- a/posix/group_member.c
+++ b/posix/group_member.c
@@ -16,9 +16,10 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
+#include <scratch_buffer.h>
+#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
-#include <stdlib.h>
#include <limits.h>
#ifndef NGROUPS_MAX
@@ -28,22 +29,26 @@
int
__group_member (gid_t gid)
{
- int n, size;
+ int n;
gid_t *groups;
+ struct scratch_buffer buf;
+ scratch_buffer_init (&buf);
+
+ n = __getgroups (0, NULL);
+ if (!scratch_buffer_set_array_size (&buf, n, sizeof (*groups)))
+ abort ();
+ groups = buf.data;
- size = NGROUPS_MAX;
- do
- {
- groups = __alloca (size * sizeof *groups);
- n = __getgroups (size, groups);
- size *= 2;
- }
- while (n == size / 2);
+ n = __getgroups (n, groups);
while (n-- > 0)
if (groups[n] == gid)
- return 1;
+ {
+ scratch_buffer_free (&buf);
+ return 1;
+ }
+ scratch_buffer_free (&buf);
return 0;
}
weak_alias (__group_member, group_member)
diff --git a/posix/tst-group_member.c b/posix/tst-group_member.c
new file mode 100644
index 0000000000..7f70841832
--- /dev/null
+++ b/posix/tst-group_member.c
@@ -0,0 +1,41 @@
+/* Basic tests for group_member.
+ Copyright (C) 2023 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/>. */
+
+#include <alloca.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <support/check.h>
+
+static int do_test (void)
+{
+ int n;
+ gid_t *groups;
+
+ n = getgroups (0, NULL);
+ groups = alloca (n * sizeof (*groups));
+ n = getgroups (n, groups);
+
+ while (n-- > 0)
+ TEST_COMPARE (1, group_member(groups[n]));
+
+ return EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>
--
2.39.2
next reply other threads:[~2023-08-08 18:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-08 18:28 Joe Simmons-Talbott [this message]
2023-08-09 9:43 ` Florian Weimer
2023-08-11 17:42 ` Siddhesh Poyarekar
2023-08-29 11:17 ` Florian Weimer
2023-09-21 16:48 ` Joe Simmons-Talbott
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