[committed 2.34, 2.35, 2.36, 2.37, 2.38] CVE-2023-4911

[committed 2.34, 2.35, 2.36, 2.37, 2.38] CVE-2023-4911

[Siddhesh Poyarekar]

Backport fixes for privilege escalation due to buffer overwrite in
tunables processing.

Thanks,
Sid

-- 
2.41.0

[committed 2.38 1/2] Propagate GLIBC_TUNABLES in setxid binaries

[Siddhesh Poyarekar]

GLIBC_TUNABLES scrubbing happens earlier than envvar scrubbing and some
tunables are required to propagate past setxid boundary, like their
env_alias.  Rely on tunable scrubbing to clean out GLIBC_TUNABLES like
before, restoring behaviour in glibc 2.37 and earlier.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit 0d5f9ea97f1b39f2a855756078771673a68497e1)
---
 sysdeps/generic/unsecvars.h | 1 -
 1 file changed, 1 deletion(-)

diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
index 81397fb90b..8278c50a84 100644
--- a/sysdeps/generic/unsecvars.h
+++ b/sysdeps/generic/unsecvars.h
@@ -4,7 +4,6 @@
 #define UNSECURE_ENVVARS \
   "GCONV_PATH\0"							      \
   "GETCONF_DIR\0"							      \
-  "GLIBC_TUNABLES\0"							      \
   "HOSTALIASES\0"							      \
   "LD_AUDIT\0"								      \
   "LD_DEBUG\0"								      \
-- 
2.41.0

[committed 2.34] tunables: Terminate if end of input is reached (CVE-2023-4911)

[Siddhesh Poyarekar]

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 e16f9968f3..625780a01a 100644
--- a/NEWS
+++ b/NEWS
@@ -55,6 +55,11 @@ 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:
 
   [11053] regex: Wrong results with backreferences
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 8009e54ee5..837474b504 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -188,11 +188,7 @@ 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.  */
@@ -252,9 +248,16 @@ 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';
 }
 #endif
 
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 05619c9adc..cd4e843640 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -52,6 +52,8 @@ 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",
@@ -70,6 +72,8 @@ 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",
+  "",
   "",
   "",
   "",
@@ -84,11 +88,18 @@ test_child (int off)
   const char *val = getenv ("GLIBC_TUNABLES");
 
 #if HAVE_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;
 #else
@@ -117,21 +128,26 @@ 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);
 
@@ -139,9 +155,14 @@ 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;
     }
 }
 
-- 
2.41.0

[committed 2.35] tunables: Terminate if end of input is reached (CVE-2023-4911)

[Siddhesh Poyarekar]

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 36da15a922..be1c4ffaee 100644
--- a/NEWS
+++ b/NEWS
@@ -97,6 +97,11 @@ 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.
+
 \f
 Version 2.35
 
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 8e7ee9df10..76cf8b9da3 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -187,11 +187,7 @@ 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.  */
@@ -251,9 +247,16 @@ 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';
 }
 #endif
 
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 88182b7b25..5e9e4c5756 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -52,6 +52,8 @@ 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",
@@ -70,6 +72,8 @@ 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",
+  "",
   "",
   "",
   "",
@@ -84,11 +88,18 @@ test_child (int off)
   const char *val = getenv ("GLIBC_TUNABLES");
 
 #if HAVE_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;
 #else
@@ -117,21 +128,26 @@ 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);
 
@@ -139,9 +155,14 @@ 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;
     }
 }
 
-- 
2.41.0

[committed 2.36] tunables: Terminate if end of input is reached (CVE-2023-4911)

[Siddhesh Poyarekar]

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 ae55ffb53a..5358e0cbe3 100644
--- a/NEWS
+++ b/NEWS
@@ -36,6 +36,11 @@ 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:
 
   [12154] Do not fail DNS resolution for CNAMEs which are not host names
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 8e7ee9df10..76cf8b9da3 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -187,11 +187,7 @@ 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.  */
@@ -251,9 +247,16 @@ 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';
 }
 #endif
 
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 88182b7b25..5e9e4c5756 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -52,6 +52,8 @@ 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",
@@ -70,6 +72,8 @@ 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",
+  "",
   "",
   "",
   "",
@@ -84,11 +88,18 @@ test_child (int off)
   const char *val = getenv ("GLIBC_TUNABLES");
 
 #if HAVE_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;
 #else
@@ -117,21 +128,26 @@ 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);
 
@@ -139,9 +155,14 @@ 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;
     }
 }
 
-- 
2.41.0

[committed 2.37] tunables: Terminate if end of input is reached (CVE-2023-4911)

[Siddhesh Poyarekar]

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 3725cc4820..b351537a78 100644
--- a/NEWS
+++ b/NEWS
@@ -31,6 +31,11 @@ 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:
 
   [20975] Deferred cancellation triggers in __check_pf and looses lock leading to deadlock
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 327b9eb52f..985b69c180 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -187,11 +187,7 @@ 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.  */
@@ -251,9 +247,16 @@ 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';
 }
 #endif
 
diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
index 807b426012..1f5e7f4f06 100644
--- a/elf/tst-env-setuid-tunables.c
+++ b/elf/tst-env-setuid-tunables.c
@@ -52,6 +52,8 @@ 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",
@@ -70,6 +72,8 @@ 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",
+  "",
   "",
   "",
   "",
@@ -84,11 +88,18 @@ test_child (int off)
   const char *val = getenv ("GLIBC_TUNABLES");
 
 #if HAVE_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;
 #else
@@ -117,21 +128,26 @@ 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);
 
@@ -139,9 +155,14 @@ 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;
     }
 }
 
-- 
2.41.0

[committed 2.38 2/2] tunables: Terminate if end of input is reached (CVE-2023-4911)

[Siddhesh Poyarekar]

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;
     }
 }
 
-- 
2.41.0