On Wed, Nov 10, 2021 at 09:28:12AM +0100, David Hildenbrand wrote: > On 08.11.21 09:38, Yafang Shao wrote: > > Make sure the string set to task comm is always nul terminated. > > > > strlcpy: "the result is always a valid NUL-terminated string that fits > in the buffer" > > The only difference seems to be that strscpy_pad() pads the remainder > with zeroes. > > Is this description correct and I am missing something important? Yes, this makes sure it's zero padded just to be robust against full tsk->comm copies that got noticed in other places. The only other change is that we want to remove strlcpy() from the kernel generally since it can trigger out-of-bound reads on the source string[1]. So, in this case, the most robust version is to use strscpy_pad(). -Kees [1] https://github.com/KSPP/linux/issues/89 > > > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> > > Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> > > Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> > > Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> > > Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > > Cc: Michal Miroslaw <mirq-linux@xxxxxxxxxxxx> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > Cc: David Hildenbrand <david@xxxxxxxxxx> > > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > > Cc: Petr Mladek <pmladek@xxxxxxxx> > > --- > > fs/exec.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/exec.c b/fs/exec.c > > index a098c133d8d7..404156b5b314 100644 > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) > > { > > task_lock(tsk); > > trace_task_rename(tsk, buf); > > - strlcpy(tsk->comm, buf, sizeof(tsk->comm)); > > + strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)); > > task_unlock(tsk); > > perf_event_comm(tsk, exec); > > } > > > > > -- > Thanks, > > David / dhildenb > -- Kees Cook
