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Commit 8099b047 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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exec: load_script: don't blindly truncate shebang string 

load_script() simply truncates bprm->buf and this is very wrong if the
length of shebang string exceeds BINPRM_BUF_SIZE-2.  This can silently
truncate i_arg or (worse) we can execute the wrong binary if buf[2:126]
happens to be the valid executable path.

Change load_script() to return ENOEXEC if it can't find '\n' or zero in
bprm->buf.  Note that '\0' can come from either
prepare_binprm()->memset() or from kernel_read(), we do not care.

Link: http://lkml.kernel.org/r/20181112160931.GA28463@redhat.com


Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Ben Woodard <woodard@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fb5bf317

fs/binfmt_script.c

+7 −3
Original line number Diff line number Diff line
@@ -42,10 +42,14 @@ static int load_script(struct linux_binprm *bprm) 
	fput(bprm->file);

	bprm->file = NULL;



	bprm->buf[BINPRM_BUF_SIZE - 1] = '\0';

	if ((cp = strchr(bprm->buf, '\n')) == NULL)

		cp = bprm->buf+BINPRM_BUF_SIZE-1;

	for (cp = bprm->buf+2;; cp++) {

		if (cp >= bprm->buf + BINPRM_BUF_SIZE)

			return -ENOEXEC;

		if (!*cp || (*cp == '\n'))

			break;

	}

	*cp = '\0';



	while (cp > bprm->buf) {

		cp--;

		if ((*cp == ' ') || (*cp == '\t'))