release/5.2.40/bpf-offload-Replace-bitwise-AND-by-logical-AND-in-bp.patch

From 5327d82d1fe46038bed1e425cfa700decdcea448 Mon Sep 17 00:00:00 2001
From: Johannes Krude <johannes@krude.de>
Date: Wed, 12 Feb 2020 20:32:27 +0100
Subject: [PATCH] bpf, offload: Replace bitwise AND by logical AND in
 bpf_prog_offload_info_fill

commit e20d3a055a457a10a4c748ce5b7c2ed3173a1324 upstream.

This if guards whether user-space wants a copy of the offload-jited
bytecode and whether this bytecode exists. By erroneously doing a bitwise
AND instead of a logical AND on user- and kernel-space buffer-size can lead
to no data being copied to user-space especially when user-space size is a
power of two and bigger then the kernel-space buffer.

Fixes: fcfb126defda ("bpf: add new jited info fields in bpf_dev_offload and bpf_prog_info")
Signed-off-by: Johannes Krude <johannes@krude.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20200212193227.GA3769@phlox.h.transitiv.net
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index ba635209ae9a..1853aa420f2f 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -321,7 +321,7 @@ int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
 
 	ulen = info->jited_prog_len;
 	info->jited_prog_len = aux->offload->jited_len;
-	if (info->jited_prog_len & ulen) {
+	if (info->jited_prog_len && ulen) {
 		uinsns = u64_to_user_ptr(info->jited_prog_insns);
 		ulen = min_t(u32, info->jited_prog_len, ulen);
 		if (copy_to_user(uinsns, aux->offload->jited_image, ulen)) {
-- 
2.7.4