CVE-2023-4911 glibc: buffer overflow in ld.so leading to privilege escalation

Resolves: RHEL-3036

glibc-RHEL-3036.patch

@@ -0,0 +1,157 @@
+This patch was developed under embargo and cannot reference an upstream
+commit. To find the associated commit please review the upstream git
+log for CVE-2023-4911 to identify the relevant commits.
+
+Author: Siddhesh Poyarekar <siddhesh@sourceware.org>
+Date:   Tue Sep 19 18:39:32 2023 -0400
+
+    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>
+
+Conflicts:
+	NEWS
+	(Dropped)
+	elf/tst-env-setuid-tunables.c
+	(Trivial conflict at HAVE_TUNABLES)
+
+diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
+index 3c84809d44381241..2c878e08ea197b29 100644
+--- a/elf/dl-tunables.c
++++ b/elf/dl-tunables.c
+@@ -193,11 +193,7 @@ 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.  */
+@@ -257,9 +253,16 @@ 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 0b9b075c40598c6f..8b0861c4ad853040 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;
+     }
+ }
+ 

glibc.spec

@@ -132,7 +132,7 @@ end \
 Summary: The GNU libc libraries
 Name: glibc
 Version: %{glibcversion}
-Release: %{glibcrelease}.6
+Release: %{glibcrelease}.7
 
 # In general, GPLv2+ is used by programs, LGPLv2+ is used for
 # libraries.
@@ -1052,6 +1052,7 @@ Patch864: glibc-rh2234714.patch
 Patch865: glibc-RHEL-2435.patch
 Patch866: glibc-RHEL-2435-2.patch
 Patch867: glibc-RHEL-2423.patch
+Patch868: glibc-RHEL-3036.patch
 
 ##############################################################################
 # Continued list of core "glibc" package information:
@@ -2882,6 +2883,9 @@ fi
 %files -f compat-libpthread-nonshared.filelist -n compat-libpthread-nonshared
 
 %changelog
+* Wed Sep 20 2023 Siddhesh Poyarekar <siddhesh@redhat.com> - 2.28-236.7
+- CVE-2023-4911 glibc: buffer overflow in ld.so leading to privilege escalation (RHEL-3036)
+
 * Tue Sep 19 2023 Carlos O'Donell <carlos@redhat.com> - 2.28-236.6
 - Revert: Always call destructors in reverse constructor order (#2233338)