pack-check.c::verify_packfile(): don't run SHA-1 update on huge data

Running the SHA1_Update() on the whole packfile in a single call
revealed an overflow problem we had in the SHA-1 implementation
on POWER architecture some time ago, which was fixed with commit
b47f509b (June 19, 2006).  Other SHA-1 implementations may have
a similar problem.

The sliding mmap() series already makes chunked calls to
SHA1_Update(), so this patch itself will become moot when it
graduates to "master", but in the meantime, run the hash
function in smaller chunks to prevent possible future problems.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/pack-check.c b/pack-check.c
index c0caaee0933382f30cc932731e1e387cc9a03c12..8e123b71ed7898d2054ed9ef729c70ed40422bc3 100644 (file)
--- a/pack-check.c
+++ b/pack-check.c
@@ -1,16 +1,18 @@
 #include "cache.h"
 #include "pack.h"
 
+#define BATCH (1u<<20)
+
 static int verify_packfile(struct packed_git *p)
 {
        unsigned long index_size = p->index_size;
        void *index_base = p->index_base;
        SHA_CTX ctx;
        unsigned char sha1[20];
-       unsigned long pack_size = p->pack_size;
-       void *pack_base;
        struct pack_header *hdr;
        int nr_objects, err, i;
+       unsigned char *packdata;
+       unsigned long datasize;
 
        /* Header consistency check */
        hdr = p->pack_base;
@@ -25,11 +27,19 @@ static int verify_packfile(struct packed_git *p)
                             "while idx size expects %d", nr_objects,
                             num_packed_objects(p));
 
+       /* Check integrity of pack data with its SHA-1 checksum */
        SHA1_Init(&ctx);
-       pack_base = p->pack_base;
-       SHA1_Update(&ctx, pack_base, pack_size - 20);
+       packdata = p->pack_base;
+       datasize = p->pack_size - 20;
+       while (datasize) {
+               unsigned long batch = (datasize < BATCH) ? datasize : BATCH;
+               SHA1_Update(&ctx, packdata, batch);
+               datasize -= batch;
+               packdata += batch;
+       }
        SHA1_Final(sha1, &ctx);
-       if (hashcmp(sha1, (unsigned char *)pack_base + pack_size - 20))
+
+       if (hashcmp(sha1, (unsigned char *)(p->pack_base) + p->pack_size - 20))
                return error("Packfile %s SHA1 mismatch with itself",
                             p->pack_name);
        if (hashcmp(sha1, (unsigned char *)index_base + index_size - 40))