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Check for syscall error in the SETXID implementation in NPTL (bug 13347).

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At this point, we can only abort the process because we have already
switched credentials on other threads.  Returning an error would still
leave the process in an inconsistent state.

The new xtest needs root privileges to run.
This commit is contained in:
Florian Weimer
2014-03-24 15:24:02 +01:00
parent c859b32e9d
commit 13f7fe35ae
4 changed files with 161 additions and 3 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2014-04-01 Florian Weimer <fweimer@redhat.com>
[BZ #13347]
* nptl/nptl-init.c (sighandler_setxid): Check system call result.
* nptl/tst-setuid2.c: New file.
* nptl/Makefile (xtests): Add tst-setuid2.
2014-04-01 Alan Modra <amodra@gmail.com>
[BZ #16786]

3
nptl/Makefile
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@ -270,7 +270,8 @@ tests = tst-typesizes \
tst-vfork1 tst-vfork2 tst-vfork1x tst-vfork2x \
tst-getpid1 tst-getpid2 tst-getpid3 \
tst-initializers1 $(patsubst %,tst-initializers1-%,c89 gnu89 c99 gnu99)
xtests = tst-setuid1 tst-setuid1-static tst-mutexpp1 tst-mutexpp6 tst-mutexpp10
xtests = tst-setuid1 tst-setuid1-static tst-setuid2 \
tst-mutexpp1 tst-mutexpp6 tst-mutexpp10
test-srcs = tst-oddstacklimit
# Files which must not be linked with libpthread.

9
nptl/nptl-init.c
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@ -232,6 +232,7 @@ sighandler_setxid (int sig, siginfo_t *si, void *ctx)
/* Determine the process ID. It might be negative if the thread is
in the middle of a fork() call. */
pid_t pid = THREAD_GETMEM (THREAD_SELF, pid);
int result;
if (__glibc_unlikely (pid < 0))
pid = -pid;
@ -245,8 +246,12 @@ sighandler_setxid (int sig, siginfo_t *si, void *ctx)
return;
INTERNAL_SYSCALL_DECL (err);
INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, err, 3, __xidcmd->id[0],
__xidcmd->id[1], __xidcmd->id[2]);
result = INTERNAL_SYSCALL_NCS (__xidcmd->syscall_no, err, 3, __xidcmd->id[0],
__xidcmd->id[1], __xidcmd->id[2]);
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err)))
/* Safety check. This should never happen if the setxid system
calls are only ever called through their glibc wrappers. */
abort ();
/* Reset the SETXID flag. */
struct pthread *self = THREAD_SELF;

145
nptl/tst-setuid2.c Normal file
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@ -0,0 +1,145 @@
/* Copyright (C) 2014 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
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <unistd.h>
/* Check that a partial setuid failure aborts the process. */
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond_send;
static void (*func_sent) (void);
static pthread_cond_t cond_recv;
#define FAIL(fmt, ...) \
do { printf ("FAIL: " fmt "\n", __VA_ARGS__); _exit (1); } while (0)
static void *
thread_func (void *ctx __attribute__ ((unused)))
{
int ret = pthread_mutex_lock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_lock (thread): %d", ret);
while (true)
{
if (func_sent != NULL)
{
void (*func) (void) = func_sent;
ret = pthread_mutex_unlock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_unlock (thread): %d", ret);
func ();
ret = pthread_mutex_lock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_lock (thread): %d", ret);
func_sent = NULL;
ret = pthread_cond_signal (&cond_recv);
if (ret != 0)
FAIL ("pthread_cond_signal (recv): %d", ret);
}
ret = pthread_cond_wait (&cond_send, &mutex);
if (ret != 0)
FAIL ("pthread_cond_wait (send): %d", ret);
}
return NULL;
}
static void
run_on_thread (void (*func) (void))
{
int ret = pthread_mutex_lock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_lock (%s): %d", __func__, ret);
func_sent = func;
ret = pthread_mutex_unlock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_unlock (%s): %d", __func__, ret);
ret = pthread_cond_signal (&cond_send);
if (ret != 0)
FAIL ("pthread_mutex_lock (%s): %d", __func__, ret);
ret = pthread_mutex_lock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_lock (%s): %d", __func__, ret);
while (func_sent != NULL)
{
ret = pthread_cond_wait (&cond_recv, &mutex);
if (ret != 0)
FAIL ("pthread_mutex_wait (%s): %d", __func__, ret);
}
ret = pthread_mutex_unlock (&mutex);
if (ret != 0)
FAIL ("pthread_mutex_unlock (%s): %d", __func__, ret);
}
static void
change_thread_ids (void)
{
long ret = syscall (__NR_setresuid, 2001, 2002, 2003);
if (ret != 0)
FAIL ("setresuid (2001, 2002, 2003): %ld", ret);
}
static uid_t ruid, euid, suid;
static void
get_thread_ids (void)
{
if (getresuid (&ruid, &euid, &suid) < 0)
FAIL ("getresuid: %m (%d)", errno);
}
static void
abort_expected (int signal __attribute__ ((unused)))
{
_exit (0);
}
static int
do_test (void)
{
pthread_t thread;
int ret = pthread_create (&thread, NULL, thread_func, NULL);
if (ret != 0)
FAIL ("pthread_create: %d", ret);
run_on_thread (change_thread_ids);
signal (SIGABRT, &abort_expected);
/* This should abort the process. */
if (setresuid (1001, 1002, 1003) < 0)
FAIL ("setresuid: %m (%d)", errno);
signal (SIGABRT, SIG_DFL);
/* If we get here, check that the kernel did the right thing. */
run_on_thread (get_thread_ids);
if (ruid != 1001 || euid != 1002 || euid != 1003)
FAIL ("unexpected UIDs after setuid: %ld, %ld, %ld",
(long) ruid, (long) euid, (long) suid);
return 0;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"