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)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 4 Jan 2019 21:13:47 +0000 (13:13 -0800)
commit8099b047ecc431518b9bb6bdbba3549bbecdc343
treef0abafbb5f20984f92165e4da26fb37377dd497a
parentfb5bf31722d0805a3f394f7d59f2e8cd07acccb7
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: 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>
fs/binfmt_script.c