glibc/patches/glibc-2.38-tunables-terminate-if-end-of-input-is-reached.patch

From 750a45a783906a19591fb8ff6b7841470f1f5701 Mon Sep 17 00:00:00 2001
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
Date: Tue, 19 Sep 2023 18:39:32 -0400
Subject: [PATCH] tunables: Terminate if end of input is reached
 (CVE-2023-4911)

The string parsing routine may end up writing beyond bounds of tunestr
if the input tunable string is malformed, of the form name=name=val.
This gets processed twice, first as name=name=val and next as name=val,
resulting in tunestr being name=name=val:name=val, thus overflowing
tunestr.

Terminate the parsing loop at the first instance itself so that tunestr
does not overflow.

This also fixes up tst-env-setuid-tunables to actually handle failures
correct and add new tests to validate the fix for this CVE.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit 1056e5b4c3f2d90ed2b4a55f96add28da2f4c8fa)
---
 NEWS                          |  5 +++++
 elf/dl-tunables.c             | 17 +++++++++-------
 elf/tst-env-setuid-tunables.c | 37 +++++++++++++++++++++++++++--------
 3 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/NEWS b/NEWS
index f1b1b0a3b4..bfcd46efa9 100644
--- a/NEWS
+++ b/NEWS
@@ -24,6 +24,11 @@ Security related changes:
   an application calls getaddrinfo for AF_INET6 with AI_CANONNAME,
   AI_ALL and AI_V4MAPPED flags set.
 
+  CVE-2023-4911: If a tunable of the form NAME=NAME=VAL is passed in the
+  environment of a setuid program and NAME is valid, it may result in a
+  buffer overflow, which could be exploited to achieve escalated
+  privileges.  This flaw was introduced in glibc 2.34.
+
 The following bugs are resolved with this release:
 
   [30723] posix_memalign repeatedly scans long bin lists
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 62b7332d95..cae67efa0a 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -180,11 +180,7 @@ parse_tunables (char *tunestr, char *valstring)
       /* If we reach the end of the string before getting a valid name-value
 	 pair, bail out.  */
       if (p[len] == '\0')
-	{
-	  if (__libc_enable_secure)
-	    tunestr[off] = '\0';
-	  return;
-	}
+	break;
 
       /* We did not find a valid name-value pair before encountering the
 	 colon.  */
@@ -244,9 +240,16 @@ parse_tunables (char *tunestr, char *valstring)
 	    }
 	}
 
-      if (p[len] != '\0')
-	p += len + 1;
+      /* We reached the end while processing the tunable string.  */
+      if (p[len] == '\0')
+	break;
+
+      p += len + 1;
     }
+
+  /* Terminate tunestr before we leave.  */
+  if (__libc_enable_secure)
+    tunestr[off] = '\0';
 }
 
 /* Enable the glibc.malloc.check tunable in SETUID/SETGID programs only when
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 7dfb0e073a..f0b92c97e7 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -50,6 +50,8 @@ const char *teststrings[] =
   "glibc.malloc.perturb=0x800:not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
   "glibc.not_valid.check=2:glibc.malloc.mmap_threshold=4096",
   "not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.check=2",
   "glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096:glibc.malloc.check=2",
   "glibc.malloc.check=4:glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096",
   ":glibc.malloc.garbage=2:glibc.malloc.check=1",
@@ -68,6 +70,8 @@ const char *resultstrings[] =
   "glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
   "glibc.malloc.mmap_threshold=4096",
   "glibc.malloc.mmap_threshold=4096",
+  "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
+  "",
   "",
   "",
   "",
@@ -81,11 +85,18 @@ test_child (int off)
 {
   const char *val = getenv ("GLIBC_TUNABLES");
 
+  printf ("    [%d] GLIBC_TUNABLES is %s\n", off, val);
+  fflush (stdout);
   if (val != NULL && strcmp (val, resultstrings[off]) == 0)
     return 0;
 
   if (val != NULL)
-    printf ("[%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
+    printf ("    [%d] Unexpected GLIBC_TUNABLES VALUE %s, expected %s\n",
+	    off, val, resultstrings[off]);
+  else
+    printf ("    [%d] GLIBC_TUNABLES environment variable absent\n", off);
+
+  fflush (stdout);
 
   return 1;
 }
@@ -106,21 +117,26 @@ do_test (int argc, char **argv)
       if (ret != 0)
 	exit (1);
 
-      exit (EXIT_SUCCESS);
+      /* Special return code to make sure that the child executed all the way
+	 through.  */
+      exit (42);
     }
   else
     {
-      int ret = 0;
-
       /* Spawn tests.  */
       for (int i = 0; i < array_length (teststrings); i++)
 	{
 	  char buf[INT_BUFSIZE_BOUND (int)];
 
-	  printf ("Spawned test for %s (%d)\n", teststrings[i], i);
+	  printf ("[%d] Spawned test for %s\n", i, teststrings[i]);
 	  snprintf (buf, sizeof (buf), "%d\n", i);
+	  fflush (stdout);
 	  if (setenv ("GLIBC_TUNABLES", teststrings[i], 1) != 0)
-	    exit (1);
+	    {
+	      printf ("    [%d] Failed to set GLIBC_TUNABLES: %m", i);
+	      support_record_failure ();
+	      continue;
+	    }
 
 	  int status = support_capture_subprogram_self_sgid (buf);
 
@@ -128,9 +144,14 @@ do_test (int argc, char **argv)
 	  if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
 	    return EXIT_UNSUPPORTED;
 
-	  ret |= status;
+	  if (WEXITSTATUS (status) != 42)
+	    {
+	      printf ("    [%d] child failed with status %d\n", i,
+		      WEXITSTATUS (status));
+	      support_record_failure ();
+	    }
 	}
-      return ret;
+      return 0;
     }
 }
 
-- 
2.39.3

1	From 750a45a783906a19591fb8ff6b7841470f1f5701 Mon Sep 17 00:00:00 2001
2	From: Siddhesh Poyarekar <siddhesh@sourceware.org>
3	Date: Tue, 19 Sep 2023 18:39:32 -0400
4	Subject: [PATCH] tunables: Terminate if end of input is reached
5	(CVE-2023-4911)
6
7	The string parsing routine may end up writing beyond bounds of tunestr
8	if the input tunable string is malformed, of the form name=name=val.
9	This gets processed twice, first as name=name=val and next as name=val,
10	resulting in tunestr being name=name=val:name=val, thus overflowing
11	tunestr.
12
13	Terminate the parsing loop at the first instance itself so that tunestr
14	does not overflow.
15
16	This also fixes up tst-env-setuid-tunables to actually handle failures
17	correct and add new tests to validate the fix for this CVE.
18
19	Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
20	Reviewed-by: Carlos O'Donell <carlos@redhat.com>
21	(cherry picked from commit 1056e5b4c3f2d90ed2b4a55f96add28da2f4c8fa)
22	---
23	NEWS \| 5 +++++
24	elf/dl-tunables.c \| 17 +++++++++-------
25	elf/tst-env-setuid-tunables.c \| 37 +++++++++++++++++++++++++++--------
26	3 files changed, 44 insertions(+), 15 deletions(-)
27
28	diff --git a/NEWS b/NEWS
29	index f1b1b0a3b4..bfcd46efa9 100644
30	--- a/NEWS
31	+++ b/NEWS
32	@@ -24,6 +24,11 @@ Security related changes:
33	an application calls getaddrinfo for AF_INET6 with AI_CANONNAME,
34	AI_ALL and AI_V4MAPPED flags set.
35
36	+ CVE-2023-4911: If a tunable of the form NAME=NAME=VAL is passed in the
37	+ environment of a setuid program and NAME is valid, it may result in a
38	+ buffer overflow, which could be exploited to achieve escalated
39	+ privileges. This flaw was introduced in glibc 2.34.
40	+
41	The following bugs are resolved with this release:
42
43	[30723] posix_memalign repeatedly scans long bin lists
44	diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
45	index 62b7332d95..cae67efa0a 100644
46	--- a/elf/dl-tunables.c
47	+++ b/elf/dl-tunables.c
48	@@ -180,11 +180,7 @@ parse_tunables (char tunestr, char valstring)
49	/* If we reach the end of the string before getting a valid name-value
50	pair, bail out. */
51	if (p[len] == '\0')
52	- {
53	- if (__libc_enable_secure)
54	- tunestr[off] = '\0';
55	- return;
56	- }
57	+ break;
58
59	/* We did not find a valid name-value pair before encountering the
60	colon. */
61	@@ -244,9 +240,16 @@ parse_tunables (char tunestr, char valstring)
62	}
63	}
64
65	- if (p[len] != '\0')
66	- p += len + 1;
67	+ /* We reached the end while processing the tunable string. */
68	+ if (p[len] == '\0')
69	+ break;
70	+
71	+ p += len + 1;
72	}
73	+
74	+ /* Terminate tunestr before we leave. */
75	+ if (__libc_enable_secure)
76	+ tunestr[off] = '\0';
77	}
78
79	/* Enable the glibc.malloc.check tunable in SETUID/SETGID programs only when
80	diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
81	index 7dfb0e073a..f0b92c97e7 100644
82	--- a/elf/tst-env-setuid-tunables.c
83	+++ b/elf/tst-env-setuid-tunables.c
84	@@ -50,6 +50,8 @@ const char *teststrings[] =
85	"glibc.malloc.perturb=0x800:not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
86	"glibc.not_valid.check=2:glibc.malloc.mmap_threshold=4096",
87	"not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
88	+ "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
89	+ "glibc.malloc.check=2",
90	"glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096:glibc.malloc.check=2",
91	"glibc.malloc.check=4:glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096",
92	":glibc.malloc.garbage=2:glibc.malloc.check=1",
93	@@ -68,6 +70,8 @@ const char *resultstrings[] =
94	"glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
95	"glibc.malloc.mmap_threshold=4096",
96	"glibc.malloc.mmap_threshold=4096",
97	+ "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
98	+ "",
99	"",
100	"",
101	"",
102	@@ -81,11 +85,18 @@ test_child (int off)
103	{
104	const char *val = getenv ("GLIBC_TUNABLES");
105
106	+ printf (" [%d] GLIBC_TUNABLES is %s\n", off, val);
107	+ fflush (stdout);
108	if (val != NULL && strcmp (val, resultstrings[off]) == 0)
109	return 0;
110
111	if (val != NULL)
112	- printf ("[%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
113	+ printf (" [%d] Unexpected GLIBC_TUNABLES VALUE %s, expected %s\n",
114	+ off, val, resultstrings[off]);
115	+ else
116	+ printf (" [%d] GLIBC_TUNABLES environment variable absent\n", off);
117	+
118	+ fflush (stdout);
119
120	return 1;
121	}
122	@@ -106,21 +117,26 @@ do_test (int argc, char **argv)
123	if (ret != 0)
124	exit (1);
125
126	- exit (EXIT_SUCCESS);
127	+ /* Special return code to make sure that the child executed all the way
128	+ through. */
129	+ exit (42);
130	}
131	else
132	{
133	- int ret = 0;
134	-
135	/* Spawn tests. */
136	for (int i = 0; i < array_length (teststrings); i++)
137	{
138	char buf[INT_BUFSIZE_BOUND (int)];
139
140	- printf ("Spawned test for %s (%d)\n", teststrings[i], i);
141	+ printf ("[%d] Spawned test for %s\n", i, teststrings[i]);
142	snprintf (buf, sizeof (buf), "%d\n", i);
143	+ fflush (stdout);
144	if (setenv ("GLIBC_TUNABLES", teststrings[i], 1) != 0)
145	- exit (1);
146	+ {
147	+ printf (" [%d] Failed to set GLIBC_TUNABLES: %m", i);
148	+ support_record_failure ();
149	+ continue;
150	+ }
151
152	int status = support_capture_subprogram_self_sgid (buf);
153
154	@@ -128,9 +144,14 @@ do_test (int argc, char **argv)
155	if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
156	return EXIT_UNSUPPORTED;
157
158	- ret \|= status;
159	+ if (WEXITSTATUS (status) != 42)
160	+ {
161	+ printf (" [%d] child failed with status %d\n", i,
162	+ WEXITSTATUS (status));
163	+ support_record_failure ();
164	+ }
165	}
166	- return ret;
167	+ return 0;
168	}
169	}
170
171	--
172	2.39.3
173