bpf: Remove bpf_probe_write_user() warning message

JIRA: https://issues.redhat.com/browse/RHEL-78201

commit b28573e
Author: Marco Elver <elver@google.com>
Date:   Fri Nov 29 09:59:33 2024 +0100

    bpf: Remove bpf_probe_write_user() warning message

    The warning message for bpf_probe_write_user() was introduced in
    96ae522 ("bpf: Add bpf_probe_write_user BPF helper to be called in
    tracers"), with the following in the commit message:

        Given this feature is meant for experiments, and it has a risk of
        crashing the system, and running programs, we print a warning on
        when a proglet that attempts to use this helper is installed,
        along with the pid and process name.

    After 8 years since 96ae522, bpf_probe_write_user() has found
    successful applications beyond experiments [1, 2], with no other good
    alternatives. Despite its intended purpose for "experiments", that
    doesn't stop Hyrum's law, and there are likely many more users depending
    on this helper: "[..] it does not matter what you promise [..] all
    observable behaviors of your system will be depended on by somebody."

    The ominous "helper that may corrupt user memory!" has offered no real
    benefit, and has been found to lead to confusion where the system
    administrator is loading programs with valid use cases.

    As such, remove the warning message.

    Link: https://lore.kernel.org/lkml/20240404190146.1898103-1-elver@google.com/ [1]
    Link: https://lore.kernel.org/r/lkml/CAAn3qOUMD81-vxLLfep0H6rRd74ho2VaekdL4HjKq+Y1t9KdXQ@mail.gmail.com/ [2]
    Link: https://lore.kernel.org/all/CAEf4Bzb4D_=zuJrg3PawMOW3KqF8JvJm9SwF81_XHR2+u5hkUg@mail.gmail.com/
    Signed-off-by: Marco Elver <elver@google.com>
    Acked-by: Jiri Olsa <jolsa@kernel.org>
    Acked-by: Daniel Borkmann <daniel@iogearbox.net>
    Link: https://lore.kernel.org/r/20241129090040.2690691-1-elver@google.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

kernel/trace/bpf_trace.c

@@ -362,9 +362,6 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
 	if (!capable(CAP_SYS_ADMIN))
 		return NULL;
 
-	pr_warn_ratelimited("%s[%d] is installing a program with bpf_probe_write_user helper that may corrupt user memory!",
-			    current->comm, task_pid_nr(current));
-
 	return &bpf_probe_write_user_proto;
 }