From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 14 Feb 2019 23:02:18 +0000 (-0800)
Subject: Revert "exec: load_script: don't blindly truncate shebang string"
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=cb5b020a8d38f77209d0472a0fea755299a8ec78;p=linux.git

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 d0078cbb718b4..7cde3f46ad263 100644
--- 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'))