Commit eb1b6688 authored Nov 02, 2019 by Daniel Borkmann Committed by Alexei Starovoitov Nov 02, 2019

bpf: Make use of probe_user_write in probe write helper

Convert the bpf_probe_write_user() helper to probe_user_write() such that
writes are not attempted under KERNEL_DS anymore which is buggy as kernel
and user space pointers can have overlapping addresses. Also, given we have
the access_ok() check inside probe_user_write(), the helper doesn't need
to do it twice.

Fixes: 96ae5227 ("bpf: Add bpf_probe_write_user BPF helper to be called in tracers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/841c461781874c07a0ee404a454c3bc0459eed30.1572649915.git.daniel@iogearbox.net

parent 75a1a607

kernel/trace/bpf_trace.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -163,7 +163,7 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
		.arg3_type = ARG_ANYTHING,
		};

		BPF_CALL_3(bpf_probe_write_user, void , unsafe_ptr, const void , src,
		BPF_CALL_3(bpf_probe_write_user, void __user , unsafe_ptr, const void , src,
		u32, size)
		{
		/*
		@@ -186,10 +186,8 @@ BPF_CALL_3(bpf_probe_write_user, void , unsafe_ptr, const void , src,
		return -EPERM;
		if (unlikely(!nmi_uaccess_okay()))
		return -EPERM;
		if (!access_ok(unsafe_ptr, size))
		return -EPERM;

		return probe_kernel_write(unsafe_ptr, src, size);
		return probe_user_write(unsafe_ptr, src, size);
		}

		static const struct bpf_func_proto bpf_probe_write_user_proto = {