Re: Crash when attaching uretprobes to processes running in Docker

Oleg Nesterov
2025-01-17T01:58:15Z

On 01/17, Masami Hiramatsu wrote:
>
> On Tue, 14 Jan 2025 15:21:29 +0100
> Jiri Olsa <olsajiri@gmail.com> wrote:
>
> > On Tue, Jan 14, 2025 at 12:21:07PM +0100, Oleg Nesterov wrote:
> > >
> > > But please not that the uretprobed function can return any value
> > > including -ENOSYS, and this is what sys_uretprobe() has to return.
> >
> > right, uretprobe syscall returns value of the uretprobed function,
> > so we can't use any reserved value
>
> We can make uretprobe (entry) fail if the return value is one of
> errno or NULL, because it *knows* what the return value here.

I fail to understand... Could you spell please?

But whatever you meant, I don't think it is right, sorry.. please
correct me.

"it *knows*". Who it? How can it know??? I'd say "it" can't know,
but probably I missed your point.

Not to mention it doesn't really matter. It is not safe to even try
to do

movq $__NR_uretprobe, %rax
syscall

if the probed task has seccomp filters.

Oleg.