1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
From: Florian Weimer <fweimer@redhat.com>
Date: Wed, 29 Apr 2015 14:41:25 +0200
Subject: [PATCH] CVE-2014-8121: Do not close NSS files database during
iteration [BZ #18007]
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Robin Hack discovered Samba would enter an infinite loop processing
certain quota-related requests. We eventually tracked this down to a
glibc issue.
Running a (simplified) test case under strace shows that /etc/passwd
is continuously opened and closed:
…
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
lseek(3, 0, SEEK_CUR) = 0
read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 2717
lseek(3, 2717, SEEK_SET) = 2717
close(3) = 0
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
lseek(3, 0, SEEK_CUR) = 0
lseek(3, 0, SEEK_SET) = 0
read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 2717
lseek(3, 2717, SEEK_SET) = 2717
close(3) = 0
open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
lseek(3, 0, SEEK_CUR) = 0
…
The lookup function implementation in
nss/nss_files/files-XXX.c:DB_LOOKUP has code to prevent that. It is
supposed skip closing the input file if it was already open.
/* Reset file pointer to beginning or open file. */ \
status = internal_setent (keep_stream); \
\
if (status == NSS_STATUS_SUCCESS) \
{ \
/* Tell getent function that we have repositioned the file pointer. */ \
last_use = getby; \
\
while ((status = internal_getent (result, buffer, buflen, errnop \
H_ERRNO_ARG EXTRA_ARGS_VALUE)) \
== NSS_STATUS_SUCCESS) \
{ break_if_match } \
\
if (! keep_stream) \
internal_endent (); \
} \
keep_stream is initialized from the stayopen flag in internal_setent.
internal_setent is called from the set*ent implementation as:
status = internal_setent (stayopen);
However, for non-host database, this flag is always 0, per the
STAYOPEN magic in nss/getXXent_r.c.
Thus, the fix is this:
- status = internal_setent (stayopen);
+ status = internal_setent (1);
This is not a behavioral change even for the hosts database (where the
application can specify the stayopen flag) because with a call to
sethostent(0), the file handle is still not closed in the
implementation of gethostent.
---
nss/Makefile | 2 +-
nss/nss_files/files-XXX.c | 2 +-
nss/tst-nss-getpwent.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 120 insertions(+), 2 deletions(-)
create mode 100644 nss/tst-nss-getpwent.c
diff --git a/nss/Makefile b/nss/Makefile
index 1fa7f1f397f5..d6f0139bf5c8 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -39,7 +39,7 @@ install-bin := getent makedb
makedb-modules = xmalloc hash-string
extra-objs += $(makedb-modules:=.o)
-tests = test-netdb tst-nss-test1 test-digits-dots
+tests = test-netdb tst-nss-test1 test-digits-dots tst-nss-getpwent
xtests = bug-erange
# Specify rules for the nss_* modules. We have some services.
diff --git a/nss/nss_files/files-XXX.c b/nss/nss_files/files-XXX.c
index 212b938fdf39..cc38174df0c2 100644
--- a/nss/nss_files/files-XXX.c
+++ b/nss/nss_files/files-XXX.c
@@ -134,7 +134,7 @@ CONCAT(_nss_files_set,ENTNAME) (int stayopen)
__libc_lock_lock (lock);
- status = internal_setent (stayopen);
+ status = internal_setent (1);
if (status == NSS_STATUS_SUCCESS && fgetpos (stream, &position) < 0)
{
diff --git a/nss/tst-nss-getpwent.c b/nss/tst-nss-getpwent.c
new file mode 100644
index 000000000000..f2e8abce6098
--- /dev/null
+++ b/nss/tst-nss-getpwent.c
@@ -0,0 +1,118 @@
+/* Copyright (C) 2015 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 <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int
+do_test (void)
+{
+ /* Count the number of entries in the password database, and fetch
+ data from the first and last entries. */
+ size_t count = 0;
+ struct passwd * pw;
+ char *first_name = NULL;
+ uid_t first_uid = 0;
+ char *last_name = NULL;
+ uid_t last_uid = 0;
+ setpwent ();
+ while ((pw = getpwent ()) != NULL)
+ {
+ if (first_name == NULL)
+ {
+ first_name = strdup (pw->pw_name);
+ if (first_name == NULL)
+ {
+ printf ("strdup: %m\n");
+ return 1;
+ }
+ first_uid = pw->pw_uid;
+ }
+
+ free (last_name);
+ last_name = strdup (pw->pw_name);
+ if (last_name == NULL)
+ {
+ printf ("strdup: %m\n");
+ return 1;
+ }
+ last_uid = pw->pw_uid;
+ ++count;
+ }
+ endpwent ();
+
+ if (count == 0)
+ {
+ printf ("No entries in the password database.\n");
+ return 0;
+ }
+
+ /* Try again, this time interleaving with name-based and UID-based
+ lookup operations. The counts do not match if the interleaved
+ lookups affected the enumeration. */
+ size_t new_count = 0;
+ setpwent ();
+ while ((pw = getpwent ()) != NULL)
+ {
+ if (new_count == count)
+ {
+ printf ("Additional entry in the password database.\n");
+ return 1;
+ }
+ ++new_count;
+ struct passwd *pw2 = getpwnam (first_name);
+ if (pw2 == NULL)
+ {
+ printf ("getpwnam (%s) failed: %m\n", first_name);
+ return 1;
+ }
+ pw2 = getpwnam (last_name);
+ if (pw2 == NULL)
+ {
+ printf ("getpwnam (%s) failed: %m\n", last_name);
+ return 1;
+ }
+ pw2 = getpwuid (first_uid);
+ if (pw2 == NULL)
+ {
+ printf ("getpwuid (%llu) failed: %m\n",
+ (unsigned long long) first_uid);
+ return 1;
+ }
+ pw2 = getpwuid (last_uid);
+ if (pw2 == NULL)
+ {
+ printf ("getpwuid (%llu) failed: %m\n",
+ (unsigned long long) last_uid);
+ return 1;
+ }
+ }
+ endpwent ();
+ if (new_count < count)
+ {
+ printf ("Missing entry in the password database.\n");
+ return 1;
+ }
+
+ return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
|
