read_index_from(): catch out of order entries when reading an index file

diff --git a/read-cache.c b/read-cache.c
index ba13353b377d4f27b9ff6cf1b85811fcca61e224..22b0add52f28cbe3c8dab727a1959d8ba72c4688 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -1438,6 +1438,21 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
        return ce;
 }
 
+static void check_ce_order(struct cache_entry *ce, struct cache_entry *next_ce)
+{
+       int name_compare = strcmp(ce->name, next_ce->name);
+       if (0 < name_compare)
+               die("unordered stage entries in index");
+       if (!name_compare) {
+               if (!ce_stage(ce))
+                       die("multiple stage entries for merged file '%s'",
+                               ce->name);
+               if (ce_stage(ce) > ce_stage(next_ce))
+                       die("unordered stage entries for '%s'",
+                               ce->name);
+       }
+}
+
 /* remember to discard_cache() before reading a different cache! */
 int read_index_from(struct index_state *istate, const char *path)
 {
@@ -1477,6 +1492,7 @@ int read_index_from(struct index_state *istate, const char *path)
        if (verify_hdr(hdr, mmap_size) < 0)
                goto unmap;
 
+       hashcpy(istate->sha1, (unsigned char *)hdr + mmap_size - 20);
        istate->version = ntohl(hdr->hdr_version);
        istate->cache_nr = ntohl(hdr->hdr_entries);
        istate->cache_alloc = alloc_nr(istate->cache_nr);
@@ -1498,6 +1514,9 @@ int read_index_from(struct index_state *istate, const char *path)
                ce = create_from_disk(disk_ce, &consumed, previous_name);
                set_index_entry(istate, i, ce);
 
+               if (i > 0)
+                       check_ce_order(istate->cache[i - 1], ce);
+
                src_offset += consumed;
        }
        strbuf_release(&previous_name_buf);
@@ -1760,6 +1779,50 @@ static int ce_write_entry(git_SHA_CTX *c, int fd, struct cache_entry *ce,
        return result;
 }
 
+/*
+ * This function verifies if index_state has the correct sha1 of the
+ * index file.  Don't die if we have any other failure, just return 0.
+ */
+static int verify_index_from(const struct index_state *istate, const char *path)
+{
+       int fd;
+       ssize_t n;
+       struct stat st;
+       unsigned char sha1[20];
+
+       if (!istate->initialized)
+               return 0;
+
+       fd = open(path, O_RDONLY);
+       if (fd < 0)
+               return 0;
+
+       if (fstat(fd, &st))
+               goto out;
+
+       if (st.st_size < sizeof(struct cache_header) + 20)
+               goto out;
+
+       n = pread_in_full(fd, sha1, 20, st.st_size - 20);
+       if (n != 20)
+               goto out;
+
+       if (hashcmp(istate->sha1, sha1))
+               goto out;
+
+       close(fd);
+       return 1;
+
+out:
+       close(fd);
+       return 0;
+}
+
+static int verify_index(const struct index_state *istate)
+{
+       return verify_index_from(istate, get_index_file());
+}
+
 static int has_racy_timestamp(struct index_state *istate)
 {
        int entries = istate->cache_nr;
@@ -1779,7 +1842,7 @@ static int has_racy_timestamp(struct index_state *istate)
 void update_index_if_able(struct index_state *istate, struct lock_file *lockfile)
 {
        if ((istate->cache_changed || has_racy_timestamp(istate)) &&
-           !write_index(istate, lockfile->fd))
+           verify_index(istate) && !write_index(istate, lockfile->fd))
                commit_locked_index(lockfile);
        else
                rollback_lock_file(lockfile);