Revert "exec: load_script: don't blindly truncate shebang string"

commit cb5b020a8d38f77209d0472a0fea755299a8ec78 upstream.

This reverts commit 8099b047ecc431518b9bb6bdbba3549bbecdc343.

It turns out that people do actually depend on the shebang string being
truncated, and on the fact that an interpreter (like perl) will often
just re-interpret it entirely to get the full argument list.

Reported-by: Samuel Dionne-Riel <samuel@dionne-riel.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c
index 634bdbb23851f0c7402c2b607a66ba92f22cd374..afdf4e3cafc2aa5f1c1ff1dc0e8cfb256c6a3b89 100644 (file)
--- a/fs/binfmt_script.c
+++ b/fs/binfmt_script.c
@@ -43,14 +43,10 @@ static int load_script(struct linux_binprm *bprm)
        fput(bprm->file);
        bprm->file = NULL;
 
-       for (cp = bprm->buf+2;; cp++) {
-               if (cp >= bprm->buf + BINPRM_BUF_SIZE)
-                       return -ENOEXEC;
-               if (!*cp || (*cp == '\n'))
-                       break;
-       }
+       bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';
+       if ((cp = strchr(bprm->buf, '\n')) == NULL)
+               cp = bprm->buf+BINPRM_BUF_SIZE-1;
        *cp = '\0';
-
        while (cp > bprm->buf) {
                cp--;
                if ((*cp == ' ') || (*cp == '\t'))