stpncpy: fix size checking [BZ #18975]

I think the last clause of the conditional,

	|| __n <= __bos (__dest)

may be backward.  The code should call the runtime-checking function
if __n is not constant, or if __n is known to be LARGER than the size
of the destination.

4 files changed, 172 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index f510bea..67d3517 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2015-08-15  Zack Weinberg  <zackw@panix.com>
+
+	[BZ #18975]
+	* string/bits/string3.h (stpncpy): Call __stpncpy_chk if the
+	buffer length is known to be too large, not if it's known to be
+	small enough.
+	* debug/tst-chk1.c (do_test): Do all tests for catching a buffer
+	overflow at runtime, involving a length parameter, twice: once
+	with a compile-time constant length parameter, once without.
+
 2015-08-14  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #18824]
diff --git a/NEWS b/NEWS
index 088969c..fbbcddb 100644
--- a/NEWS
+++ b/NEWS
@@ -10,8 +10,8 @@ Version 2.23
 * The following bugs are resolved with this release:
 
   16517, 16519, 16520, 16734, 17905, 18086, 18265, 18480, 18525, 18618,
-  18647, 18661, 18674, 18778, 18781, 18787, 18789, 18790, 18820, 18824.
-
+  18647, 18661, 18674, 18778, 18781, 18787, 18789, 18790, 18820, 18824,
+  18975.
 
 Version 2.22
 
diff --git a/debug/tst-chk1.c b/debug/tst-chk1.c
index 53559e6..bded583 100644
--- a/debug/tst-chk1.c
+++ b/debug/tst-chk1.c
@@ -264,21 +264,39 @@ do_test (void)
 #endif
 
 #if __USE_FORTIFY_LEVEL >= 1
-  /* Now check if all buffer overflows are caught at runtime.  */
+  /* Now check if all buffer overflows are caught at runtime.
+     N.B. All tests involving a length parameter need to be done
+     twice: once with the length a compile-time constant, once without.  */
+
+  CHK_FAIL_START
+  memcpy (buf + 1, "abcdefghij", 10);
+  CHK_FAIL_END
 
   CHK_FAIL_START
   memcpy (buf + 1, "abcdefghij", l0 + 10);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  memmove (buf + 2, buf + 1, 9);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   memmove (buf + 2, buf + 1, l0 + 9);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  p = (char *) mempcpy (buf + 6, "abcde", 5);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   p = (char *) mempcpy (buf + 6, "abcde", l0 + 5);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  memset (buf + 9, 'j', 2);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   memset (buf + 9, 'j', l0 + 2);
   CHK_FAIL_END
 
@@ -291,10 +309,18 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  strncpy (buf + 7, "X", 4);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   strncpy (buf + 7, "X", l0 + 4);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  stpncpy (buf + 6, "cd", 5);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   stpncpy (buf + 6, "cd", l0 + 5);
   CHK_FAIL_END
 
@@ -304,6 +330,10 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  snprintf (buf + 8, 3, "%d", num2);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   snprintf (buf + 8, l0 + 3, "%d", num2);
   CHK_FAIL_END
 
@@ -316,29 +346,50 @@ do_test (void)
   CHK_FAIL_END
 # endif
 
-  memcpy (buf, str1 + 2, l0 + 9);
+  memcpy (buf, str1 + 2, 9);
   CHK_FAIL_START
   strcat (buf, "AB");
   CHK_FAIL_END
 
-  memcpy (buf, str1 + 3, l0 + 8);
+  memcpy (buf, str1 + 3, 8);
+  CHK_FAIL_START
+  strncat (buf, "ZYXWV", 3);
+  CHK_FAIL_END
+
+  memcpy (buf, str1 + 3, 8);
   CHK_FAIL_START
   strncat (buf, "ZYXWV", l0 + 3);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  memcpy (a.buf1 + 1, "abcdefghij", 10);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   memcpy (a.buf1 + 1, "abcdefghij", l0 + 10);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  memmove (a.buf1 + 2, a.buf1 + 1, 9);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   memmove (a.buf1 + 2, a.buf1 + 1, l0 + 9);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  p = (char *) mempcpy (a.buf1 + 6, "abcde", 5);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   p = (char *) mempcpy (a.buf1 + 6, "abcde", l0 + 5);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  memset (a.buf1 + 9, 'j', 2);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   memset (a.buf1 + 9, 'j', l0 + 2);
   CHK_FAIL_END
 
@@ -357,6 +408,10 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  strncpy (a.buf1 + (O + 6), "X", 4);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   strncpy (a.buf1 + (O + 6), "X", l0 + 4);
   CHK_FAIL_END
 
@@ -366,16 +421,20 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  snprintf (a.buf1 + (O + 7), 3, "%d", num2);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   snprintf (a.buf1 + (O + 7), l0 + 3, "%d", num2);
   CHK_FAIL_END
 # endif
 
-  memcpy (a.buf1, str1 + (3 - O), l0 + 8 + O);
+  memcpy (a.buf1, str1 + (3 - O), 8 + O);
   CHK_FAIL_START
   strcat (a.buf1, "AB");
   CHK_FAIL_END
 
-  memcpy (a.buf1, str1 + (4 - O), l0 + 7 + O);
+  memcpy (a.buf1, str1 + (4 - O), 7 + O);
   CHK_FAIL_START
   strncat (a.buf1, "ZYXWV", l0 + 3);
   CHK_FAIL_END
@@ -504,25 +563,47 @@ do_test (void)
 #endif
 
 #if __USE_FORTIFY_LEVEL >= 1
-  /* Now check if all buffer overflows are caught at runtime.  */
+  /* Now check if all buffer overflows are caught at runtime.
+     N.B. All tests involving a length parameter need to be done
+     twice: once with the length a compile-time constant, once without.  */
+
+  CHK_FAIL_START
+  wmemcpy (wbuf + 1, L"abcdefghij", 10);
+  CHK_FAIL_END
 
   CHK_FAIL_START
   wmemcpy (wbuf + 1, L"abcdefghij", l0 + 10);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wmemcpy (wbuf + 9, L"abcdefghij", 10);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wmemcpy (wbuf + 9, L"abcdefghij", l0 + 10);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wmemmove (wbuf + 2, wbuf + 1, 9);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wmemmove (wbuf + 2, wbuf + 1, l0 + 9);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wp = wmempcpy (wbuf + 6, L"abcde", 5);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wp = wmempcpy (wbuf + 6, L"abcde", l0 + 5);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wmemset (wbuf + 9, L'j', 2);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wmemset (wbuf + 9, L'j', l0 + 2);
   CHK_FAIL_END
 
@@ -535,6 +616,10 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wcsncpy (wbuf + 7, L"X", 4);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wcsncpy (wbuf + 7, L"X", l0 + 4);
   CHK_FAIL_END
 
@@ -547,32 +632,52 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wcpncpy (wbuf + 6, L"cd", 5);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wcpncpy (wbuf + 6, L"cd", l0 + 5);
   CHK_FAIL_END
 
-  wmemcpy (wbuf, wstr1 + 2, l0 + 9);
+  wmemcpy (wbuf, wstr1 + 2, 9);
   CHK_FAIL_START
   wcscat (wbuf, L"AB");
   CHK_FAIL_END
 
-  wmemcpy (wbuf, wstr1 + 3, l0 + 8);
+  wmemcpy (wbuf, wstr1 + 3, 8);
   CHK_FAIL_START
   wcsncat (wbuf, L"ZYXWV", l0 + 3);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wmemcpy (wa.buf1 + 1, L"abcdefghij", 10);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wmemcpy (wa.buf1 + 1, L"abcdefghij", l0 + 10);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wmemmove (wa.buf1 + 2, wa.buf1 + 1, 9);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wmemmove (wa.buf1 + 2, wa.buf1 + 1, l0 + 9);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wp = wmempcpy (wa.buf1 + 6, L"abcde", 5);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wp = wmempcpy (wa.buf1 + 6, L"abcde", l0 + 5);
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wmemset (wa.buf1 + 9, L'j', 2);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wmemset (wa.buf1 + 9, L'j', l0 + 2);
   CHK_FAIL_END
 
@@ -591,15 +696,19 @@ do_test (void)
   CHK_FAIL_END
 
   CHK_FAIL_START
+  wcsncpy (wa.buf1 + (O + 6), L"X", 4);
+  CHK_FAIL_END
+
+  CHK_FAIL_START
   wcsncpy (wa.buf1 + (O + 6), L"X", l0 + 4);
   CHK_FAIL_END
 
-  wmemcpy (wa.buf1, wstr1 + (3 - O), l0 + 8 + O);
+  wmemcpy (wa.buf1, wstr1 + (3 - O), 8 + O);
   CHK_FAIL_START
   wcscat (wa.buf1, L"AB");
   CHK_FAIL_END
 
-  wmemcpy (wa.buf1, wstr1 + (4 - O), l0 + 7 + O);
+  wmemcpy (wa.buf1, wstr1 + (4 - O), 7 + O);
   CHK_FAIL_START
   wcsncat (wa.buf1, L"ZYXWV", l0 + 3);
   CHK_FAIL_END
@@ -884,6 +993,11 @@ do_test (void)
   if (read (fileno (stdin), buf, sizeof (buf) + 1) != sizeof (buf) + 1)
     FAIL ();
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  if (read (fileno (stdin), buf, l0 + sizeof (buf) + 1) != sizeof (buf) + 1)
+    FAIL ();
+  CHK_FAIL_END
 #endif
 
   if (pread (fileno (stdin), buf, sizeof (buf) - 1, sizeof (buf) - 2)
@@ -904,6 +1018,12 @@ do_test (void)
       != sizeof (buf) + 1)
     FAIL ();
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  if (pread (fileno (stdin), buf, l0 + sizeof (buf) + 1, 2 * sizeof (buf))
+      != sizeof (buf) + 1)
+    FAIL ();
+  CHK_FAIL_END
 #endif
 
   if (pread64 (fileno (stdin), buf, sizeof (buf) - 1, sizeof (buf) - 2)
@@ -924,6 +1044,12 @@ do_test (void)
       != sizeof (buf) + 1)
     FAIL ();
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  if (pread64 (fileno (stdin), buf, l0 + sizeof (buf) + 1, 2 * sizeof (buf))
+      != sizeof (buf) + 1)
+    FAIL ();
+  CHK_FAIL_END
 #endif
 
   if (freopen (temp_filename, "r", stdin) == NULL)
@@ -1435,23 +1561,38 @@ do_test (void)
 
   fd_set s;
   FD_ZERO (&s);
+
   FD_SET (FD_SETSIZE - 1, &s);
 #if __USE_FORTIFY_LEVEL >= 1
   CHK_FAIL_START
   FD_SET (FD_SETSIZE, &s);
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  FD_SET (l0 + FD_SETSIZE, &s);
+  CHK_FAIL_END
 #endif
+
   FD_CLR (FD_SETSIZE - 1, &s);
 #if __USE_FORTIFY_LEVEL >= 1
   CHK_FAIL_START
   FD_CLR (FD_SETSIZE, &s);
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  FD_SET (l0 + FD_SETSIZE, &s);
+  CHK_FAIL_END
 #endif
+
   FD_ISSET (FD_SETSIZE - 1, &s);
 #if __USE_FORTIFY_LEVEL >= 1
   CHK_FAIL_START
   FD_ISSET (FD_SETSIZE, &s);
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  FD_ISSET (l0 + FD_SETSIZE, &s);
+  CHK_FAIL_END
 #endif
 
   struct pollfd fds[1];
@@ -1462,12 +1603,20 @@ do_test (void)
   CHK_FAIL_START
   poll (fds, 2, 0);
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  poll (fds, l0 + 2, 0);
+  CHK_FAIL_END
 #endif
   ppoll (fds, 1, NULL, NULL);
 #if __USE_FORTIFY_LEVEL >= 1
   CHK_FAIL_START
   ppoll (fds, 2, NULL, NULL);
   CHK_FAIL_END
+
+  CHK_FAIL_START
+  ppoll (fds, l0 + 2, NULL, NULL);
+  CHK_FAIL_END
 #endif
 
   return ret;
diff --git a/string/bits/string3.h b/string/bits/string3.h
index f482935..4d11aa6 100644
--- a/string/bits/string3.h
+++ b/string/bits/string3.h
@@ -136,7 +136,7 @@ __fortify_function char *
 __NTH (stpncpy (char *__dest, const char *__src, size_t __n))
 {
   if (__bos (__dest) != (size_t) -1
-      && (!__builtin_constant_p (__n) || __n <= __bos (__dest)))
+      && (!__builtin_constant_p (__n) || __n > __bos (__dest)))
     return __stpncpy_chk (__dest, __src, __n, __bos (__dest));
   return __stpncpy_alias (__dest, __src, __n);
 }