[PATCH] nptl improve tst-context1.c to catch buffer overruns, 2nd

[Steve Munroe <sjmunroe at us dot ibm dot com>]

Oops attached the wrong patch the previous email this topic. This email 
includes the correct patch.

This patch improves the coverage of tst-context1.c to check for buffer 
overruns of the ucontext struct in the get/swapcontext functions.

Defined a new struct tst_context_t to append guard words following each 
ucontext_t in the ctx array.  Function tf() initializes the guard words 
and uc_link before calls to makecontext and swapcontext.  Then fct() can 
check for any changes to the guard words and verify that uc_link is 
still valid.

2004-06-15  Steven Munroe  <sjmunroe@us.ibm.com>

	* tst-context1.c (GUARD_PATTERN): Defined.
	(tst_context_t): Define struct containing ucontext_t & guard words.
	(ctx): Declare as an array of tst_context_t.
	(fct): Verify uc_link & guard words are still valid.
	(tf): Initialize guard words in ctx.  Adjust ctx refs for new struct.


diff -urN libc23-cvstip-20040607/nptl/tst-context1.c libc23-ppcvmx-20040607/nptl/tst-context1.c
--- libc23-cvstip-20040607/nptl/tst-context1.c	2004-04-04 05:52:05.000000000 -0500
+++ libc23-ppcvmx-20040607/nptl/tst-context1.c	2004-06-15 12:53:54.497023192 -0500
@@ -25,11 +25,20 @@
 #include <stdlib.h>
 #include <ucontext.h>
 
-
 #define N	4
+#if __WORDSIZE == 64
+#define GUARD_PATTERN 0xdeadbeafdeadbeaf
+#else
+#define GUARD_PATTERN 0xdeadbeaf
+#endif
+
+typedef struct {
+       ucontext_t uctx;
+       unsigned long	guard[3];
+   } tst_context_t;
 
 static char stacks[N][PTHREAD_STACK_MIN];
-static ucontext_t ctx[N][2];
+static tst_context_t ctx[N][2];
 static volatile int failures;
 
 
@@ -42,6 +51,29 @@
   printf ("%ld: in %s now, on_stack = %p\n", n, __FUNCTION__, on_stack);
   errno = 0;
 
+  if (ctx[n][1].uctx.uc_link != &ctx[n][0].uctx)
+    {
+      printf ("context[%ld][1] uc_link damaged, = %p\n", n,
+	      ctx[n][1].uctx.uc_link);
+      exit (1);
+    }
+
+  if ((ctx[n][0].guard[0] != GUARD_PATTERN)
+  ||  (ctx[n][0].guard[1] != GUARD_PATTERN)
+  ||  (ctx[n][0].guard[2] != GUARD_PATTERN))
+    {
+      printf ("%ld: %s context[0] overflow detected!\n", n, __FUNCTION__);
+      ++failures;
+    }
+
+  if ((ctx[n][1].guard[0] != GUARD_PATTERN)
+  ||  (ctx[n][1].guard[1] != GUARD_PATTERN)
+  ||  (ctx[n][1].guard[2] != GUARD_PATTERN))
+    {
+      printf ("%ld: %s context[1] overflow detected!\n", n, __FUNCTION__);
+      ++failures;
+    }
+
   if (n < 0 || n >= N)
     {
       printf ("%ld out of range\n", n);
@@ -61,7 +93,15 @@
 {
   int n = (int) (long int) arg;
 
-  if (getcontext (&ctx[n][1]) != 0)
+  ctx[n][0].guard[0] = GUARD_PATTERN;
+  ctx[n][0].guard[1] = GUARD_PATTERN;
+  ctx[n][0].guard[2] = GUARD_PATTERN;
+
+  ctx[n][1].guard[0] = GUARD_PATTERN;
+  ctx[n][1].guard[1] = GUARD_PATTERN;
+  ctx[n][1].guard[2] = GUARD_PATTERN;
+
+  if (getcontext (&ctx[n][1].uctx) != 0)
     {
       printf ("%d: cannot get context: %m\n", n);
       exit (1);
@@ -69,14 +109,14 @@
 
   printf ("%d: %s: before makecontext\n", n, __FUNCTION__);
 
-  ctx[n][1].uc_stack.ss_sp = stacks[n];
-  ctx[n][1].uc_stack.ss_size = PTHREAD_STACK_MIN;
-  ctx[n][1].uc_link = &ctx[n][0];
-  makecontext (&ctx[n][1], (void (*) (void)) fct, 1, (long int) n);
+  ctx[n][1].uctx.uc_stack.ss_sp = stacks[n];
+  ctx[n][1].uctx.uc_stack.ss_size = PTHREAD_STACK_MIN;
+  ctx[n][1].uctx.uc_link = &ctx[n][0].uctx;
+  makecontext (&ctx[n][1].uctx, (void (*) (void)) fct, 1, (long int) n);
 
   printf ("%d: %s: before swapcontext\n", n, __FUNCTION__);
 
-  if (swapcontext (&ctx[n][0], &ctx[n][1]) != 0)
+  if (swapcontext (&ctx[n][0].uctx, &ctx[n][1].uctx) != 0)
     {
       ++failures;
       printf ("%d: %s: swapcontext failed\n", n, __FUNCTION__);