[Bug-cpio] [PATCH 2/2] newc copyout: translate inode numbers

[Zdeněk Pavlas]

Inode numbers are truncated when building cpio archives on systems
with 64bit ino_t.  Copyin code uses these numbers when nlink > 1
to identify hardlink sets.

There is a 1 : 4Gi chance that hardlink sets A+B => I1 and C+D => I2
unpack as A+B+C+D => I2 instead.  With 20k hardlinks and 10k inodes
the probability of collision is over 1%.

This patch works around the problem by renumbering hardlinked inodes
with a 1-based sequence.  Hardlinks to the same inode are already
grouped so it's quite simple.
---
 src/copyout.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/src/copyout.c b/src/copyout.c
index d8c19a0..a60352d 100644
--- a/src/copyout.c
+++ b/src/copyout.c
@@ -241,6 +241,8 @@ writeout_defered_file (struct cpio_file_stat *header, int 
out_file_des)
    never see the "last" link to the file, so at the end we just write 
    all of the leftover defered files into the archive.  */
 
+static ino_t xlated_ino = 0;
+
 static void
 writeout_final_defers (int out_des)
 {
@@ -248,6 +250,8 @@ writeout_final_defers (int out_des)
     {
       struct deferment *h, *d;
       struct deferment **tail = &deferouts;
+
+      ++xlated_ino;
       for (h = d = deferouts; (d = d->next) != NULL;)
         {
           if (d->header.c_ino     == h->header.c_ino
@@ -334,7 +338,7 @@ write_out_new_ascii_header (const char *magic_string,
   char *p;
 
   p = stpcpy (ascii_header, magic_string);
-  to_ascii_or_warn (p, file_hdr->c_ino, 8, LG_16,
+  to_ascii_or_error (p, file_hdr->c_nlink > 1 ? xlated_ino : 0, 8, LG_16,
                    file_hdr->c_name, _("inode number"));
   p += 8;
   to_ascii_or_warn (p, file_hdr->c_mode, 8, LG_16, file_hdr->c_name,
@@ -710,6 +714,7 @@ process_copy_out ()
                {
                  if (last_link (&file_hdr) )
                    {
+                      ++xlated_ino;
                      writeout_other_defers (&file_hdr, out_file_des);
                    }
                  else
-- 
1.7.4.4