[PATCH v6] posix: Deprecate group_member for Linux
Joe Simmons-Talbott
josimmon@redhat.com
Tue Dec 12 16:56:47 GMT 2023
The alloca usage in group_member could lead to stack overflow on Linux.
Removing the alloca usage would require group_member to handle the error
condition where memory could not be allocated and that cannot be done
since group_member returns a boolean value. Thus deprecate group_member.
Add an internal only implementation of __group_member2 using a
scratch_buffer and return -1 for memory allocation errors. Use
__group_member2 for in place of __group_member internally. Add testcases
for both group_member and __group_member2.
---
Changes to v5:
* Add __group_member2 and use it internally in the place of the now
deprecated group_member.
* Add a testcase for __group_member2.
Changes to v4:
* Rebase onto latest commit.
Changes to v3:
* Fix include guards to match file location _BITS_GROUP_MEMBER_H
* Fix indentation of preprocessor directives
Changes to v2:
* Move the linux group_member.h to the bits directory
* Include the correct group_member.h in posix/unistd.h
Changes to v1:
* Add NEWS entry
* Move group_member.h to bits/group_member.h
* Include bits/group_member.h in installed headers
* Add tests to group_member.h files to only be included from unistd.h
NEWS | 4 ++
bits/group_member.h | 31 +++++++++++++++
include/unistd.h | 1 +
posix/Makefile | 8 ++++
posix/group_member.c | 32 +++++++++++++++
posix/tst-group_member.c | 41 ++++++++++++++++++++
posix/tst-group_member2.c | 43 +++++++++++++++++++++
posix/unistd.h | 6 +--
sysdeps/posix/euidaccess.c | 9 ++++-
sysdeps/unix/sysv/linux/bits/group_member.h | 32 +++++++++++++++
sysdeps/unix/sysv/linux/faccessat.c | 8 +++-
11 files changed, 209 insertions(+), 6 deletions(-)
create mode 100644 bits/group_member.h
create mode 100644 posix/tst-group_member.c
create mode 100644 posix/tst-group_member2.c
create mode 100644 sysdeps/unix/sysv/linux/bits/group_member.h
diff --git a/NEWS b/NEWS
index 9432564444..c1f9e5d0cc 100644
--- a/NEWS
+++ b/NEWS
@@ -44,6 +44,10 @@ Deprecated and removed features, and other changes affecting compatibility:
".tmp", to avoid examining temporary files created by the RPM and dpkg
package managers.
+* Deprecated group_member on Linux as it uses alloca to allocate a large
+ buffer and has no capability for indicating failure for other memory
+ allocations.
+
Changes to build and runtime requirements:
* Building on LoongArch requires at a minimum binutils 2.41 for vector
diff --git a/bits/group_member.h b/bits/group_member.h
new file mode 100644
index 0000000000..7c43e7ee06
--- /dev/null
+++ b/bits/group_member.h
@@ -0,0 +1,31 @@
+/* group_member declaration
+ 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/>. */
+
+#ifndef _UNISTD_H
+# error "Never use <bits/group_member.h> directly; include <unistd.h> instead."
+#endif
+
+#ifndef _BITS_GROUP_MEMBER_H
+# define _BITS_GROUP_MEMBER_H 1
+
+# ifdef __USE_GNU
+/* Return nonzero iff the calling process is in group GID. */
+extern int group_member (__gid_t __gid) __THROW;
+# endif
+
+#endif /* _BITS_GROUP_MEMBER_H */
diff --git a/include/unistd.h b/include/unistd.h
index e241603b81..39d5bda372 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -131,6 +131,7 @@ extern __gid_t __getegid (void) attribute_hidden;
extern int __getgroups (int __size, __gid_t __list[]) attribute_hidden;
libc_hidden_proto (__getpgid)
extern int __group_member (__gid_t __gid) attribute_hidden;
+extern int __group_member2 (__gid_t __gid) attribute_hidden;
extern int __setuid (__uid_t __uid);
extern int __setreuid (__uid_t __ruid, __uid_t __euid);
extern int __setgid (__gid_t __gid);
diff --git a/posix/Makefile b/posix/Makefile
index 3ab124d040..c4948e3980 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -29,6 +29,7 @@ headers := \
bits/getopt_core.h \
bits/getopt_ext.h \
bits/getopt_posix.h \
+ bits/group_member.h \
bits/local_lim.h \
bits/mman_ext.h \
bits/posix1_lim.h \
@@ -291,6 +292,7 @@ tests := \
tst-glob_symlinks \
tst-gnuglob \
tst-gnuglob64 \
+ tst-group_member \
tst-mmap \
tst-mmap-offset \
tst-nanosleep \
@@ -479,6 +481,10 @@ tests-special += \
# tests-special
endif
+# This test calls __group_member2 directly, which is not exported from glibc.
+tests-internal += tst-group_member2
+tests-static += tst-group_member2
+
include ../Rules
ifeq ($(run-built-tests),yes)
@@ -606,6 +612,8 @@ bug-glob1-ARGS = "$(objpfx)"
tst-execvp3-ARGS = --test-dir=$(objpfx)
CFLAGS-tst-spawn3.c += -DOBJPFX=\"$(objpfx)\"
+CFLAGS-tst-group_member.c += -Wno-error=deprecated-declarations
+
# Test voluntarily overflows struct dirent
CFLAGS-bug-glob2.c += $(no-fortify-source)
diff --git a/posix/group_member.c b/posix/group_member.c
index 22422b1f9f..576386494e 100644
--- a/posix/group_member.c
+++ b/posix/group_member.c
@@ -18,6 +18,7 @@
#include <sys/types.h>
#include <unistd.h>
+#include <scratch_buffer.h>
#include <stdlib.h>
#include <limits.h>
@@ -47,3 +48,34 @@ __group_member (gid_t gid)
return 0;
}
weak_alias (__group_member, group_member)
+
+int
+__group_member2 (gid_t gid)
+{
+ int n, size;
+ gid_t *groups;
+ struct scratch_buffer sbuf;
+ scratch_buffer_init (&sbuf);
+
+ size = NGROUPS_MAX;
+ do
+ {
+ if (!scratch_buffer_set_array_size (&sbuf, sizeof (*groups), size))
+ return -1;
+ groups = sbuf.data;
+
+ n = __getgroups (size, groups);
+ size *= 2;
+ }
+ while (n == size / 2);
+
+ while (n-- > 0)
+ if (groups[n] == gid)
+ {
+ scratch_buffer_free (&sbuf);
+ return 1;
+ }
+
+ scratch_buffer_free (&sbuf);
+ return 0;
+}
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>
diff --git a/posix/tst-group_member2.c b/posix/tst-group_member2.c
new file mode 100644
index 0000000000..ee448c578a
--- /dev/null
+++ b/posix/tst-group_member2.c
@@ -0,0 +1,43 @@
+/* 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 <posix/unistd.h>
+
+#include <support/check.h>
+
+extern int __group_member2 (__gid_t __gid);
+
+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_member2(groups[n]));
+
+ return EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>
diff --git a/posix/unistd.h b/posix/unistd.h
index 0477527a60..b65d4c63d0 100644
--- a/posix/unistd.h
+++ b/posix/unistd.h
@@ -710,10 +710,10 @@ extern __gid_t getegid (void) __THROW;
of its supplementary groups in LIST and return the number written. */
extern int getgroups (int __size, __gid_t __list[]) __THROW __wur
__fortified_attr_access (__write_only__, 2, 1);
+
#ifdef __USE_GNU
-/* Return nonzero iff the calling process is in group GID. */
-extern int group_member (__gid_t __gid) __THROW;
-#endif
+# include <bits/group_member.h>
+#endif
/* Set the user ID of the calling process to UID.
If the calling process is the super-user, set the real
diff --git a/sysdeps/posix/euidaccess.c b/sysdeps/posix/euidaccess.c
index 2282a0a8dd..2eb9db4c95 100644
--- a/sysdeps/posix/euidaccess.c
+++ b/sysdeps/posix/euidaccess.c
@@ -81,7 +81,7 @@ extern int errno;
#ifdef _LIBC
-# define group_member __group_member
+# define group_member __group_member2
# define euidaccess __euidaccess
#else
@@ -167,9 +167,14 @@ euidaccess (const char *path, int mode)
|| (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
return 0;
+ int gm = group_member (stats.st_gid);
+ if (euid != stats.st_uid && egid != stats.st_gid)
+ if (gm == -1)
+ return -1;
+
if (euid == stats.st_uid)
granted = (unsigned int) (stats.st_mode & (mode << 6)) >> 6;
- else if (egid == stats.st_gid || group_member (stats.st_gid))
+ else if (egid == stats.st_gid || gm)
granted = (unsigned int) (stats.st_mode & (mode << 3)) >> 3;
else
granted = (stats.st_mode & mode);
diff --git a/sysdeps/unix/sysv/linux/bits/group_member.h b/sysdeps/unix/sysv/linux/bits/group_member.h
new file mode 100644
index 0000000000..0dd9505c76
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/group_member.h
@@ -0,0 +1,32 @@
+/* group_member declaration
+ 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/>. */
+
+#ifndef _UNISTD_H
+# error "Never use <bits/group_member.h> directly; include <unistd.h> instead."
+#endif
+
+#ifndef _BITS_GROUP_MEMBER_H
+# define _BITS_GROUP_MEMBER_H 1
+
+# ifdef __USE_GNU
+/* Return nonzero iff the calling process is in group GID. Deprecated */
+extern int group_member (__gid_t __gid) __THROW
+ __attribute_deprecated_msg__ ("may overflow the stack");
+# endif
+
+#endif /* _BITS_GROUP_MEMBER_H */
diff --git a/sysdeps/unix/sysv/linux/faccessat.c b/sysdeps/unix/sysv/linux/faccessat.c
index 0ccbd778b5..f28ab0a6f4 100644
--- a/sysdeps/unix/sysv/linux/faccessat.c
+++ b/sysdeps/unix/sysv/linux/faccessat.c
@@ -59,11 +59,17 @@ __faccessat (int fd, const char *file, int mode, int flag)
|| (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
return 0;
+ int gm = __group_member2 (stats.st_gid);
+ if (uid != stats.st_uid &&
+ (stats.st_gid != ((flag & AT_EACCESS) ? __getegid () : __getgid ())))
+ if (gm == -1)
+ return -1;
+
int granted = (uid == stats.st_uid
? (unsigned int) (stats.st_mode & (mode << 6)) >> 6
: (stats.st_gid == ((flag & AT_EACCESS)
? __getegid () : __getgid ())
- || __group_member (stats.st_gid))
+ || gm)
? (unsigned int) (stats.st_mode & (mode << 3)) >> 3
: (stats.st_mode & mode));
--
2.41.0
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