On 01/12, Michal Hocko wrote:

On Mon 11-01-21 09:06:22, Suren Baghdasaryan wrote:

quoted

What we want is the ability for one process to influence another process
in order to optimize performance across the entire system while leaving
the security boundary intact.
Replace PTRACE_MODE_ATTACH with a combination of PTRACE_MODE_READ
and CAP_SYS_NICE. PTRACE_MODE_READ to prevent leaking ASLR metadata
and CAP_SYS_NICE for influencing process performance.

I have to say that ptrace modes are rather obscure to me. So I cannot
really judge whether MODE_READ is sufficient. My understanding has
always been that this is requred to RO access to the address space. But
this operation clearly has a visible side effect. Do we have any actual
documentation for the existing modes?

I would be really curious to hear from Jann and Oleg (now Cced).

Can't comment, sorry. I never understood these security checks and never tried.
IIUC only selinux/etc can treat ATTACH/READ differently and I have no idea what
is the difference.

Oleg.