Fix read-cache.c collission check logic.

Not only did it test the #define the wrong way around, but
it also leaked file descriptors and VM space. This should
fix it.

diff --git a/read-cache.c b/read-cache.c
index e3d3ddb..8e90d2c 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -233,6 +233,33 @@ int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
        return 0;
 }
 
+static inline int collision_check(char *filename, void *buf, unsigned int size)
+{
+#ifdef COLLISION_CHECK
+       void *map;
+       int fd = open(filename, O_RDONLY);
+       struct stat st;
+       int cmp;
+
+       /* Unreadable object, or object went away? Strange. */
+       if (fd < 0)
+               return -1;
+
+       if (fstat(fd, &st) < 0 || size != st.st_size)
+               return -1;
+
+       map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+       close(fd);
+       if (map == MAP_FAILED)
+               return -1;
+       cmp = memcmp(buf, map, size);
+       munmap(map, size);
+       if (cmp)
+               return -1;
+#endif
+       return 0;
+}
+
 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 {
        char *filename = sha1_file_name(sha1);
@@ -240,21 +267,11 @@ int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 
        fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
        if (fd < 0) {
-               void *map;
-
                if (errno != EEXIST)
                        return -1;
-#ifndef COLLISION_CHECK
-               fd = open(filename, O_RDONLY);
-               if (fd < 0)
-                       return -1;
-               map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
-               if (map == MAP_FAILED)
-                       return -1;
-               if (memcmp(buf, map, size))
+               if (collision_check(filename, buf, size))
                        return error("SHA1 collision detected!"
                                        " This is bad, bad, BAD!\a\n");
-#endif
                return 0;
        }
        write(fd, buf, size);