On Tue, Jun 15, 2021 at 12:33 PM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > > Andrei Vagin <avagin@xxxxxxxxx> writes: > > > Without this fix, if we try to run a script that contains only the > > interpreter line, the interpreter is executed with one extra empty > > argument. > > > > The code is written so that i_end has to be set to the end of valuable > > data in the buffer. > > Out of curiosity how did you spot this change in behavior? gVisor tests started failing with this change: https://github.com/google/gvisor/blob/5e05950c1c520724e2e03963850868befb95efeb/test/syscalls/linux/exec.cc#L307 We run these tests on Ubuntu 20.04 and this is the reason why we caught this issue just a few days ago. > > > Fixes: ccbb18b67323 ("exec/binfmt_script: Don't modify bprm->buf and then return -ENOEXEC") > > Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > > Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx> > > --- > > fs/binfmt_script.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/fs/binfmt_script.c b/fs/binfmt_script.c > > index 1b6625e95958..e242680f96e1 100644 > > --- a/fs/binfmt_script.c > > +++ b/fs/binfmt_script.c > > @@ -68,6 +68,9 @@ static int load_script(struct linux_binprm *bprm) > > if (!next_terminator(i_end, buf_end)) > > return -ENOEXEC; > > i_end = buf_end; > > + /* Trim zero bytes from i_end */ > > + while (i_end[-1] == 0) > > + i_end--; > > } > > /* Trim any trailing spaces/tabs from i_end */ > > while (spacetab(i_end[-1]))
