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;

     }

 }