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

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>

diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c
index d0078cb..7cde3f4 100644 (file)
--- a/fs/binfmt_script.c
+++ b/fs/binfmt_script.c
@@ -42,14 +42,10 @@ 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'))