Protect against integer overflow in malloca() calls.

7 files changed, 21 insertions, 14 deletions

diff --git a/lib/c-strcasestr.c b/lib/c-strcasestr.c
index 76732d20ff..36b2a9f5ce 100644
--- a/lib/c-strcasestr.c
+++ b/lib/c-strcasestr.c
@@ -37,7 +37,7 @@ knuth_morris_pratt (const char *haystack, const char *needle,
   size_t m = strlen (needle);
 
   /* Allocate the table.  */
-  size_t *table = (size_t *) malloca (m * sizeof (size_t));
+  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
   if (table == NULL)
     return false;
   /* Fill the table.
diff --git a/lib/c-strstr.c b/lib/c-strstr.c
index 58ae2c51cf..3652100e62 100644
--- a/lib/c-strstr.c
+++ b/lib/c-strstr.c
@@ -36,7 +36,7 @@ knuth_morris_pratt (const char *haystack, const char *needle,
   size_t m = strlen (needle);
 
   /* Allocate the table.  */
-  size_t *table = (size_t *) malloca (m * sizeof (size_t));
+  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
   if (table == NULL)
     return false;
   /* Fill the table.
diff --git a/lib/malloca.h b/lib/malloca.h
index 2f74b96170..5bb2d47348 100644
--- a/lib/malloca.h
+++ b/lib/malloca.h
@@ -70,9 +70,19 @@ extern void freea (void *p);
 # define freea free
 #endif
 
-/* Maybe we should also define a variant
-    nmalloca (size_t n, size_t s) - behaves like malloca (n * s)
-   If this would be useful in your application. please speak up.  */
+/* nmalloca(N,S) is an overflow-safe variant of malloca (N * S).
+   It allocates an array of N objects, each with S bytes of memory,
+   on the stack.  S must be positive and N must be nonnegative.
+   The array must be freed using freea() before the function returns.  */
+#if 1
+/* Cf. the definition of xalloc_oversized.  */
+# define nmalloca(n, s) \
+    ((n) > (size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) \
+     ? NULL \
+     : malloca ((n) * (s)))
+#else
+extern void * nmalloca (size_t n, size_t s);
+#endif
 
 
 #ifdef __cplusplus
diff --git a/lib/mbscasestr.c b/lib/mbscasestr.c
index a5491e4c9b..7205cca1e9 100644
--- a/lib/mbscasestr.c
+++ b/lib/mbscasestr.c
@@ -42,7 +42,7 @@ knuth_morris_pratt_unibyte (const char *haystack, const char *needle,
   size_t m = strlen (needle);
 
   /* Allocate the table.  */
-  size_t *table = (size_t *) malloca (m * sizeof (size_t));
+  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
   if (table == NULL)
     return false;
   /* Fill the table.
@@ -164,7 +164,7 @@ knuth_morris_pratt_multibyte (const char *haystack, const char *needle,
   size_t *table;
 
   /* Allocate room for needle_mbchars and the table.  */
-  char *memory = (char *) malloca (m * (sizeof (mbchar_t) + sizeof (size_t)));
+  char *memory = (char *) nmalloca (m, sizeof (mbchar_t) + sizeof (size_t));
   if (memory == NULL)
     return false;
   needle_mbchars = (mbchar_t *) memory;
diff --git a/lib/mbsstr.c b/lib/mbsstr.c
index f875207184..420be08436 100644
--- a/lib/mbsstr.c
+++ b/lib/mbsstr.c
@@ -39,7 +39,7 @@ knuth_morris_pratt_unibyte (const char *haystack, const char *needle,
   size_t m = strlen (needle);
 
   /* Allocate the table.  */
-  size_t *table = (size_t *) malloca (m * sizeof (size_t));
+  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
   if (table == NULL)
     return false;
   /* Fill the table.
@@ -160,7 +160,7 @@ knuth_morris_pratt_multibyte (const char *haystack, const char *needle,
   size_t *table;
 
   /* Allocate room for needle_mbchars and the table.  */
-  char *memory = (char *) malloca (m * (sizeof (mbchar_t) + sizeof (size_t)));
+  char *memory = (char *) nmalloca (m, sizeof (mbchar_t) + sizeof (size_t));
   if (memory == NULL)
     return false;
   needle_mbchars = (mbchar_t *) memory;
diff --git a/lib/memmem.c b/lib/memmem.c
index b7f3e12c6c..57c6560323 100644
--- a/lib/memmem.c
+++ b/lib/memmem.c
@@ -39,10 +39,7 @@ knuth_morris_pratt (const char *haystack, const char *last_haystack,
                     const char **resultp)
 {
   /* Allocate the table.  */
-  size_t *table;
-  if ((size_t) -1 / sizeof (size_t) < m)
-    return false;
-  table = (size_t *) malloca (m * sizeof (size_t));
+  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
   if (table == NULL)
     return false;
   /* Fill the table.
diff --git a/lib/strcasestr.c b/lib/strcasestr.c
index 27145dd37d..dfbf925b79 100644
--- a/lib/strcasestr.c
+++ b/lib/strcasestr.c
@@ -39,7 +39,7 @@ knuth_morris_pratt (const char *haystack, const char *needle,
   size_t m = strlen (needle);
 
   /* Allocate the table.  */
-  size_t *table = (size_t *) malloca (m * sizeof (size_t));
+  size_t *table = (size_t *) nmalloca (m, sizeof (size_t));
   if (table == NULL)
     return false;
   /* Fill the table.