entry.c: fix possible buffer overflow in remove_subtree()

remove_subtree() manipulated path in a fixed-size buffer even though
the length of the input, let alone the length of entries within the
directory, were not known in advance.  Change the function to take a
strbuf argument and use that object as its scratch space.

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

diff --git a/entry.c b/entry.c
index 20d291918f540e411916a86f56826946afacb10b..fa0e5ec8ae2c6f6d68ad0d0a8df5ae1a2085d523 100644 (file)
--- a/entry.c
+++ b/entry.c
@@ -44,33 +44,33 @@ static void create_directories(const char *path, int path_len,
        free(buf);
 }
 
-static void remove_subtree(const char *path)
+static void remove_subtree(struct strbuf *path)
 {
-       DIR *dir = opendir(path);
+       DIR *dir = opendir(path->buf);
        struct dirent *de;
-       char pathbuf[PATH_MAX];
-       char *name;
+       int origlen = path->len;
 
        if (!dir)
-               die_errno("cannot opendir '%s'", path);
-       strcpy(pathbuf, path);
-       name = pathbuf + strlen(path);
-       *name++ = '/';
+               die_errno("cannot opendir '%s'", path->buf);
        while ((de = readdir(dir)) != NULL) {
                struct stat st;
+
                if (is_dot_or_dotdot(de->d_name))
                        continue;
-               strcpy(name, de->d_name);
-               if (lstat(pathbuf, &st))
-                       die_errno("cannot lstat '%s'", pathbuf);
+
+               strbuf_addch(path, '/');
+               strbuf_addstr(path, de->d_name);
+               if (lstat(path->buf, &st))
+                       die_errno("cannot lstat '%s'", path->buf);
                if (S_ISDIR(st.st_mode))
-                       remove_subtree(pathbuf);
-               else if (unlink(pathbuf))
-                       die_errno("cannot unlink '%s'", pathbuf);
+                       remove_subtree(path);
+               else if (unlink(path->buf))
+                       die_errno("cannot unlink '%s'", path->buf);
+               strbuf_setlen(path, origlen);
        }
        closedir(dir);
-       if (rmdir(path))
-               die_errno("cannot rmdir '%s'", path);
+       if (rmdir(path->buf))
+               die_errno("cannot rmdir '%s'", path->buf);
 }
 
 static int create_file(const char *path, unsigned int mode)
@@ -271,7 +271,7 @@ int checkout_entry(struct cache_entry *ce,
                                return 0;
                        if (!state->force)
                                return error("%s is a directory", path.buf);
-                       remove_subtree(path.buf);
+                       remove_subtree(&path);
                } else if (unlink(path.buf))
                        return error("unable to unlink old '%s' (%s)",
                                     path.buf, strerror(errno));