exec: load_script: don't blindly truncate shebang string
authorOleg Nesterov <oleg@redhat.com>
Thu, 3 Jan 2019 23:28:07 +0000 (15:28 -0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 12 Feb 2019 18:47:20 +0000 (19:47 +0100)
commitab5f7407125778bb05274f4a6999c67c4a72d927
treefc6805fcd45a17e7d48154bf84a0f82762c29fdb
parent9cb8f8088d9a105af7e763a315771e39eb8c16a4
exec: load_script: don't blindly truncate shebang string

[ Upstream commit 8099b047ecc431518b9bb6bdbba3549bbecdc343 ]

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: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Ben Woodard <woodard@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
fs/binfmt_script.c