Re: error: wrong index file size in /usr/local/src/jffs2_mtd_patches/.git/objects/pack/pack-da39a3ee5e6b4b0d32 55bfef95601890afd80709.idx

[Linus Torvalds <torvalds@linux-foundation.org>]

On Tue, 26 Jun 2007, Tjernlund wrote:
>
> Did this and got a small error that I don't think should be there:

Heh. I think I see what's wrong..

> Indexing 0 objects...
> remote: Total 0 (delta 0), reused 0 (delta 0)

Ok, there were no objects that weren't in the reference repo. So far so 
good.

But:

> error: wrong index file size in /usr/local/src/jffs2_mtd_patches/.git/objects/pack/pack-da39a3ee5e6b4b0d3255bfef95601890afd80709.idx

I think this is because of that zero size:

                /*
                 * Minimum size:
                 *  - 8 bytes of header
                 *  - 256 index entries 4 bytes each
                 *  - 20-byte sha1 entry * nr
                 *  - 4-byte crc entry * nr
                 *  - 4-byte offset entry * nr
                 *  - 20-byte SHA1 of the packfile
                 *  - 20-byte SHA1 file checksum
                 * And after the 4-byte offset table might be a
                 * variable sized table containing 8-byte entries
                 * for offsets larger than 2^31.
                 */
                unsigned long min_size = 8 + 4*256 + nr*(20 + 4 + 4) + 20 + 20;
                if (idx_size < min_size || idx_size > min_size + (nr - 1)*8) {

Notice the "(nr - 1)*8" thing. And notice how "nr-1" underflows when nr is 
zero..

I bet it goes away if you remove the "-1", or if you do something like 
this (totally untested!) patch.

		Linus

---
diff --git a/sha1_file.c b/sha1_file.c
index 7628ee9..f2b1ae0 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -510,7 +510,10 @@ static int check_packed_git_idx(const char *path,  struct packed_git *p)
 		 * for offsets larger than 2^31.
 		 */
 		unsigned long min_size = 8 + 4*256 + nr*(20 + 4 + 4) + 20 + 20;
-		if (idx_size < min_size || idx_size > min_size + (nr - 1)*8) {
+		unsigned long max_size = min_size;
+		if (nr)
+			max_size += (nr - 1)*8;
+		if (idx_size < min_size || idx_size > max_size) {
 			munmap(idx_map, idx_size);
 			return error("wrong index file size in %s", path);
 		}