netdev - [PATCH] bpf_prog_offload_info_fill: replace bitwise AND by logical AND

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Message-ID: <20200212193227.GA3769@phlox.h.transitiv.net>
Date:   Wed, 12 Feb 2020 20:32:27 +0100
From:   Johannes Krude <johannes@...de.de>
To:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        trivial@...nel.org
Subject: [PATCH] bpf_prog_offload_info_fill: replace bitwise AND by logical
 AND

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.

Signed-off-by: Johannes Krude <johannes@...de.de>
---
 kernel/bpf/offload.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 2c5dc6541..bd09290e3 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)) {
-- 
2.24.0