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Fix potential hanging of gethostbyaddr_r/gethostbyname_r
When "reorder" resolver option is enabled, threads of a multi-threaded process could hang in gethostbyaddr_r, gethostbyname_r, or gethostbyname2_r. Due to a trivial bug in _res_hconf_reorder_addrs, simultaneous invocations of this function in a multi-threaded process could result to _res_hconf_reorder_addrs returning without releasing the lock it holds, causing other threads to block indefinitely while waiting for the lock that is not going to be released. [BZ #17977] * resolv/res_hconf.c (_res_hconf_reorder_addrs): Fix unlocking when initializing interface list, based on the bug analysis and the patch proposed by Eric Newton. * resolv/tst-res_hconf_reorder.c: New test. * resolv/Makefile [$(have-thread-library) = yes] (tests): Add tst-res_hconf_reorder. ($(objpfx)tst-res_hconf_reorder): Depend on $(libdl) and $(shared-thread-library). (tst-res_hconf_reorder-ENV): New variable.
This commit is contained in:
Dmitry V. Levin
parent
47852c972d
commit
b57525f1a3
11
ChangeLog
11
ChangeLog
@ -1,5 +1,16 @@
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2015-06-23 Dmitry V. Levin <ldv@altlinux.org>
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[BZ #17977]
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* resolv/res_hconf.c (_res_hconf_reorder_addrs): Fix unlocking
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when initializing interface list, based on the bug analysis
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and the patch proposed by Eric Newton.
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* resolv/tst-res_hconf_reorder.c: New test.
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* resolv/Makefile [$(have-thread-library) = yes] (tests): Add
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tst-res_hconf_reorder.
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($(objpfx)tst-res_hconf_reorder): Depend on $(libdl)
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and $(shared-thread-library).
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(tst-res_hconf_reorder-ENV): New variable.
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* resolv/res_hconf.c (_res_hconf_reorder_addrs): Fix typo
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in comment.
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20
NEWS
20
NEWS
@ -14,16 +14,16 @@ Version 2.22
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16560, 16704, 16783, 16850, 17053, 17090, 17195, 17269, 17293, 17322,
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17523, 17542, 17569, 17581, 17588, 17596, 17620, 17621, 17628, 17631,
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17692, 17711, 17715, 17776, 17779, 17792, 17836, 17912, 17916, 17930,
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17932, 17944, 17949, 17964, 17965, 17967, 17969, 17978, 17987, 17991,
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17996, 17998, 17999, 18007, 18019, 18020, 18029, 18030, 18032, 18034,
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18036, 18038, 18039, 18042, 18043, 18046, 18047, 18049, 18068, 18080,
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18093, 18100, 18104, 18110, 18111, 18116, 18125, 18128, 18138, 18185,
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18196, 18197, 18206, 18210, 18211, 18217, 18220, 18221, 18234, 18244,
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18247, 18287, 18319, 18324, 18333, 18346, 18397, 18409, 18410, 18412,
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18418, 18422, 18434, 18444, 18468, 18469, 18470, 18479, 18483, 18495,
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18496, 18497, 18498, 18507, 18512, 18513, 18519, 18520, 18522, 18527,
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18528, 18529, 18530, 18532, 18533, 18534, 18536, 18539, 18540, 18542,
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18544, 18545, 18546, 18547, 18553, 18558, 18569.
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17932, 17944, 17949, 17964, 17965, 17967, 17969, 17977, 17978, 17987,
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17991, 17996, 17998, 17999, 18007, 18019, 18020, 18029, 18030, 18032,
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18034, 18036, 18038, 18039, 18042, 18043, 18046, 18047, 18049, 18068,
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18080, 18093, 18100, 18104, 18110, 18111, 18116, 18125, 18128, 18138,
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18185, 18196, 18197, 18206, 18210, 18211, 18217, 18220, 18221, 18234,
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18244, 18247, 18287, 18319, 18324, 18333, 18346, 18397, 18409, 18410,
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18412, 18418, 18422, 18434, 18444, 18468, 18469, 18470, 18479, 18483,
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18495, 18496, 18497, 18498, 18507, 18512, 18513, 18519, 18520, 18522,
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18527, 18528, 18529, 18530, 18532, 18533, 18534, 18536, 18539, 18540,
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18542, 18544, 18545, 18546, 18547, 18553, 18558, 18569.
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* Cache information can be queried via sysconf() function on s390 e.g. with
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_SC_LEVEL1_ICACHE_SIZE as argument.
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@ -39,6 +39,7 @@ extra-libs := libresolv libnss_dns
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ifeq ($(have-thread-library),yes)
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extra-libs += libanl
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routines += gai_sigqueue
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tests += tst-res_hconf_reorder
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endif
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extra-libs-others = $(extra-libs)
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libresolv-routines := gethnamaddr res_comp res_debug \
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@ -98,6 +99,9 @@ $(objpfx)libanl.so: $(shared-thread-library)
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$(objpfx)ga_test: $(objpfx)libanl.so $(shared-thread-library)
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$(objpfx)tst-res_hconf_reorder: $(libdl) $(shared-thread-library)
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tst-res_hconf_reorder-ENV = RESOLV_REORDER=on
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$(objpfx)tst-leaks: $(objpfx)libresolv.so
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tst-leaks-ENV = MALLOC_TRACE=$(objpfx)tst-leaks.mtrace
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$(objpfx)mtrace-tst-leaks.out: $(objpfx)tst-leaks.out
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@ -473,10 +473,10 @@ _res_hconf_reorder_addrs (struct hostent *hp)
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errno = save;
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num_ifs = new_num_ifs;
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__libc_lock_unlock (lock);
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}
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__libc_lock_unlock (lock);
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__close (sd);
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}
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112
resolv/tst-res_hconf_reorder.c
Normal file
112
resolv/tst-res_hconf_reorder.c
Normal file
@ -0,0 +1,112 @@
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/* BZ #17977 _res_hconf_reorder_addrs test.
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Copyright (C) 2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stdio.h>
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#include <string.h>
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#include <time.h>
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#include <dlfcn.h>
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#include <pthread.h>
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#include <netdb.h>
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#include <netinet/in.h>
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#include <sys/socket.h>
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static struct timespec ts;
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/* The first thread that gets a lock in _res_hconf_reorder_addrs()
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should hold the lock long enough to make two other threads blocked.
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This is achieved by slowing down realloc(3) that is called several times
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by _res_hconf_reorder_addrs(). */
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void *
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realloc (void *ptr, size_t len)
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{
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static void *(*fun) (void *, size_t);
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if (!fun)
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fun = dlsym (RTLD_NEXT, "realloc");
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if (ts.tv_nsec)
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nanosleep (&ts, NULL);
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return (*fun) (ptr, len);
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}
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static void *
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resolve (void *arg)
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{
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struct in_addr addr;
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struct hostent ent;
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struct hostent *result;
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int err;
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char buf[1024];
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addr.s_addr = htonl (INADDR_LOOPBACK);
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(void) gethostbyaddr_r ((void *) &addr, sizeof (addr), AF_INET,
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&ent, buf, sizeof (buf), &result, &err);
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return arg;
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}
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static int
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do_test (void)
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{
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#define N 3
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pthread_t thr[N];
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unsigned int i;
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int result = 0;
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/* turn on realloc slowdown */
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ts.tv_nsec = 100000000;
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for (i = 0; i < N; ++i)
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{
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int rc = pthread_create (&thr[i], NULL, resolve, NULL);
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if (rc)
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{
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printf ("pthread_create: %s\n", strerror(rc));
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exit (1);
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}
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}
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for (i = 0; i < N; ++i)
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{
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void *retval;
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int rc = pthread_join (thr[i], &retval);
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if (rc)
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{
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printf ("pthread_join: %s\n", strerror(rc));
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exit (1);
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}
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if (retval)
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{
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printf ("thread %u exit status %p\n", i, retval);
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result = 1;
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}
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}
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/* turn off realloc slowdown, no longer needed */
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ts.tv_nsec = 0;
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return result;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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