Include assert.h.

(fillrand): Add a parameter, size_max.
Add an assertion.
Adjust caller.
(dopass): Break out of the `for (;;)' loop if size < offset.
That can happen now that dopass is called with SIZE == -1.
(do_wipefd): Accept a length of zero only for a regular file.
If lseek fails or returns 0 for a non-regular file, let dopass
determine the length.
Inspired by a patch from Alan Iwi.

diff --git a/src/shred.c b/src/shred.c
index c523d097b5c42431a5b119264afc661eab31d8e3..9c1262fb85215ca9e36d366e7861c060fda6d3b3 100644 (file)
--- a/src/shred.c
+++ b/src/shred.c
@@ -83,6 +83,7 @@
 
 #include <getopt.h>
 #include <stdio.h>
+#include <assert.h>
 #include <setjmp.h>
 #include <signal.h>
 #include <sys/types.h>
@@ -990,13 +991,14 @@ fillpattern (int type, unsigned char *r, size_t size)
 }
 
 /*
- * Fill a buffer with random data.
- * size is rounded UP to a multiple of ISAAC_BYTES.
+ * Fill a buffer, R (of size SIZE_MAX), with random data.
+ * SIZE is rounded UP to a multiple of ISAAC_BYTES.
  */
 static void
-fillrand (struct isaac_state *s, word32 *r, size_t size)
+fillrand (struct isaac_state *s, word32 *r, size_t size_max, size_t size)
 {
   size = (size + ISAAC_BYTES - 1) / ISAAC_BYTES;
+  assert (size <= size_max);
 
   while (size--)
     {
@@ -1083,12 +1085,14 @@ dopass (int fd, char const *qname, off_t *sizep, int type,
       lim = sizeof r;
       if ((off_t) lim > size - offset && size != -1)
        {
+         if (size < offset)
+           break;
          lim = (size_t) (size - offset);
          if (!lim)
            break;
        }
       if (type < 0)
-       fillrand (s, r, lim);
+       fillrand (s, r, sizeof r, lim);
       /* Loop to retry partial writes. */
       for (soff = 0; soff < lim; soff += ssize)
        {
@@ -1422,17 +1426,33 @@ do_wipefd (int fd, char const *qname, struct isaac_state *s,
   size = flags->size;
   if (size == -1)
     {
-      size = (S_ISREG (st.st_mode)
-             ? st.st_size
-             : lseek (fd, (off_t) 0, SEEK_END));
-      if (size < (S_ISREG (st.st_mode) ? 0 : -1))
+      /* Accept a length of zero only if it's a regular file.
+        For any other type of file, try to get the size another way.  */
+      if (S_ISREG (st.st_mode))
        {
-         error (0, 0, _("%s: file has negative size"), qname);
-         return -1;
+         size = st.st_size;
+         if (size < 0)
+           {
+             error (0, 0, _("%s: file has negative size"), qname);
+             return -1;
+           }
        }
+      else
+       {
+         size = lseek (fd, (off_t) 0, SEEK_END);
+         if (size <= 0)
+           {
+             /* We are unable to determine the length, up front.
+                Let dopass do that as part of its first iteration.  */
+             size = -1;
+           }
+       }
+
       if (0 <= size && !(flags->exact))
        {
          size += ST_BLKSIZE (st) - 1 - (size - 1) % ST_BLKSIZE (st);
+
+         /* If in rounding up, we've just overflowed, use the maximum.  */
          if (size < 0)
            size = TYPE_MAXIMUM (off_t);
        }