[PATCH] Fix crash on open of nonexisting tar/cpio file, fix cpio trailer detection

[Christian Franke]

Two issues found in current CVS:

1. Booting a grub2-mkrescue floppy crashes if 
"(memdisk)/boot/grub/grub.cfg" does not exist. This is because 
grub_cpio_open does not set grub_errno if a file does not exist.

2. The cpio format may not work. Header scan finishes early if data size 
is empty (directory, empty file). The cpio format uses the name 
"TRAILER!!!" to mark the last block.

This patch fixes both issues.


"grub-mkrescue --image-type=floppy" now works with both tar and cpio 
memdisk. Cpio was tested with this change to grub-mkrescue:

-  tar -C ${aux_dir} -cf ${memdisk_img} boot
+  ( cd ${aux_dir} && find boot | cpio -o > ${memdisk_img} )


Open issues not fixed in this patch:

- Directory detection relies on a trailing '/' in path name. This works 
for typical tar files, but not for cpio. As a consequence, tab 
completion and "ls -l" are not correct. The "mode" in the header should 
be checked instead.

- CPIO would not work on big endian architectures yet.


Christian

2008-02-05  Christian Franke  <address@hidden>

        * fs/cpio.c (grub_cpio_find_file): Return GRUB_ERR_NONE
        and (*ofs = 0) instead of GRUB_ERR_FILE_NOT_FOUND on last
        block of a cpio or tar stream.
        Check for "TRAILER!!!" instead of any empty data
        block to detect last block of a cpio stream.
        (grub_cpio_dir): Fix constness of variable np.
        (grub_cpio_open): Return GRUB_ERR_FILE_NOT_FOUND if
        cpio or tar trailer is detected.  This fixes a crash
        on open of a non existing file.


--- grub2.orig/fs/cpio.c        2008-02-03 20:29:51.718750000 +0100
+++ grub2/fs/cpio.c     2008-02-05 22:59:50.031250000 +0100
@@ -98,11 +98,6 @@ grub_cpio_find_file (struct grub_cpio_da
        return grub_error (GRUB_ERR_BAD_FS, "Invalid cpio archive");
 
       data->size = (((grub_uint32_t) hd.filesize_1) << 16) + hd.filesize_2;
-      if (data->size == 0)
-       {
-         *ofs = 0;
-         return GRUB_ERR_FILE_NOT_FOUND;
-       }
 
       if (hd.namesize & 1)
        hd.namesize++;
@@ -117,6 +112,13 @@ grub_cpio_find_file (struct grub_cpio_da
          return grub_errno;
        }
 
+      if (data->size == 0 && hd.mode == 0 && hd.namesize == 11 + 1
+         && ! grub_memcmp(*name, "TRAILER!!!", 11))
+       {
+         *ofs = 0;
+         return GRUB_ERR_NONE;
+       }
+
       data->dofs = data->hofs + sizeof (hd) + hd.namesize;
       *ofs = data->dofs + data->size;
       if (data->size & 1)
@@ -133,7 +135,7 @@ grub_cpio_find_file (struct grub_cpio_da
       if (!hd.name[0])
        {
          *ofs = 0;
-         return GRUB_ERR_FILE_NOT_FOUND;
+         return GRUB_ERR_NONE;
        }
 
       if (grub_memcmp (hd.magic, MAGIC_USTAR, sizeof (MAGIC_USTAR) - 1))
@@ -188,7 +190,8 @@ grub_cpio_dir (grub_device_t device, con
 {
   struct grub_cpio_data *data;
   grub_uint32_t ofs;
-  char *prev, *name, *np;
+  char *prev, *name;
+  const char *np;
   int len;
 
 #ifndef GRUB_UTIL
@@ -275,7 +278,10 @@ grub_cpio_open (grub_file_t file, const 
        goto fail;
 
       if (!ofs)
-       break;
+       {
+         grub_error (GRUB_ERR_FILE_NOT_FOUND, "file not found");
+         break;
+       }
 
       if (grub_strcmp (name + 1, fn) == 0)
        {