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 d0078cbb718b4855dc520dbfae91223d499da81a..7cde3f46ad263ab084aafaefa14161902f33d4f1 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'))