tree 971757f2fe3c35eea754baf518b74281000d3f4e
parent 34ccd72d633c283e4bc782f4806717341e6239b3
author Edgar Arriaga <edgararriaga@google.com> 1610407188 -0800
committer Edgar Arriaga <edgararriaga@google.com> 1612381388 -0800

FROMLIST: mm/madvise: replace ptrace attach requirement for process_madvise

process_madvise currently requires ptrace attach capability.
PTRACE_MODE_ATTACH gives one process complete control over another
process. It effectively removes the security boundary between the
two processes (in one direction). Granting ptrace attach capability
even to a system process is considered dangerous since it creates an
attack surface. This severely limits the usage of this API.
The operations process_madvise can perform do not affect the correctness
of the operation of the target process; they only affect where the data
is physically located (and therefore, how fast it can be accessed).
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.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Link: https://lore.kernel.org/lkml/202101111033.2D03EA97@keescook/T/#u

Test: built and flashed kernel
Bug: 153444106
Signed-off-by: Edgar Arriaga Garcia <edgararriaga@google.com>
Change-Id: I3624a8b0697d70f23587c1dcb746ba753c301f45