prune-packed: use strbuf to avoid having to worry about PATH_MAX

A/very/long/path/to/.git that becomes exactly PATH_MAX bytes long
after suffixed with /objects/??/??38-hex??, would have overflown
the on-stack pathname[] buffer.

Noticed-by:  Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/prune-packed.c b/builtin/prune-packed.c
index fa6ce42f44f82d34299f2dc0109be4d831cb3d48..fcf5fb6129c05156c7fd7bbb22ac380dbd0b3245 100644 (file)
--- a/builtin/prune-packed.c
+++ b/builtin/prune-packed.c
@@ -10,58 +10,62 @@ static const char * const prune_packed_usage[] = {
 
 static struct progress *progress;
 
-static void prune_dir(int i, DIR *dir, char *pathname, int len, int opts)
+static void prune_dir(int i, DIR *dir, struct strbuf *pathname, int opts)
 {
        struct dirent *de;
        char hex[40];
+       int top_len = pathname->len;
 
        sprintf(hex, "%02x", i);
        while ((de = readdir(dir)) != NULL) {
                unsigned char sha1[20];
                if (strlen(de->d_name) != 38)
                        continue;
-               memcpy(hex+2, de->d_name, 38);
+               memcpy(hex + 2, de->d_name, 38);
                if (get_sha1_hex(hex, sha1))
                        continue;
                if (!has_sha1_pack(sha1))
                        continue;
-               memcpy(pathname + len, de->d_name, 38);
+
+               strbuf_add(pathname, de->d_name, 38);
                if (opts & PRUNE_PACKED_DRY_RUN)
-                       printf("rm -f %s\n", pathname);
+                       printf("rm -f %s\n", pathname->buf);
                else
-                       unlink_or_warn(pathname);
+                       unlink_or_warn(pathname->buf);
                display_progress(progress, i + 1);
+               strbuf_setlen(pathname, top_len);
        }
 }
 
 void prune_packed_objects(int opts)
 {
        int i;
-       static char pathname[PATH_MAX];
        const char *dir = get_object_directory();
-       int len = strlen(dir);
+       struct strbuf pathname = STRBUF_INIT;
+       int top_len;
 
+       strbuf_addstr(&pathname, dir);
        if (opts & PRUNE_PACKED_VERBOSE)
                progress = start_progress_delay("Removing duplicate objects",
                        256, 95, 2);
 
-       if (len > PATH_MAX - 42)
-               die("impossible object directory");
-       memcpy(pathname, dir, len);
-       if (len && pathname[len-1] != '/')
-               pathname[len++] = '/';
+       if (pathname.len && pathname.buf[pathname.len - 1] != '/')
+               strbuf_addch(&pathname, '/');
+
+       top_len = pathname.len;
        for (i = 0; i < 256; i++) {
                DIR *d;
 
                display_progress(progress, i + 1);
-               sprintf(pathname + len, "%02x/", i);
-               d = opendir(pathname);
+               strbuf_setlen(&pathname, top_len);
+               strbuf_addf(&pathname, "%02x/", i);
+               d = opendir(pathname.buf);
                if (!d)
                        continue;
-               prune_dir(i, d, pathname, len + 3, opts);
+               prune_dir(i, d, &pathname, opts);
                closedir(d);
-               pathname[len + 2] = '\0';
-               rmdir(pathname);
+               strbuf_setlen(&pathname, top_len + 2);
+               rmdir(pathname.buf);
        }
        stop_progress(&progress);
 }