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Message-Id: <20190919214811.535877836@linuxfoundation.org>
Date: Fri, 20 Sep 2019 00:03:29 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Ilya Leoshkevich <iii@...ux.ibm.com>,
Daniel Borkmann <daniel@...earbox.net>,
Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 44/79] bpf: allow narrow loads of some sk_reuseport_md fields with offset > 0
From: Ilya Leoshkevich <iii@...ux.ibm.com>
[ Upstream commit 2c238177bd7f4b14bdf7447cc1cd9bb791f147e6 ]
test_select_reuseport fails on s390 due to verifier rejecting
test_select_reuseport_kern.o with the following message:
; data_check.eth_protocol = reuse_md->eth_protocol;
18: (69) r1 = *(u16 *)(r6 +22)
invalid bpf_context access off=22 size=2
This is because on big-endian machines casts from __u32 to __u16 are
generated by referencing the respective variable as __u16 with an offset
of 2 (as opposed to 0 on little-endian machines).
The verifier already has all the infrastructure in place to allow such
accesses, it's just that they are not explicitly enabled for
eth_protocol field. Enable them for eth_protocol field by using
bpf_ctx_range instead of offsetof.
Ditto for ip_protocol, bind_inany and len, since they already allow
narrowing, and the same problem can arise when working with them.
Fixes: 2dbb9b9e6df6 ("bpf: Introduce BPF_PROG_TYPE_SK_REUSEPORT")
Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
net/core/filter.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index c996380f29597..e6fa88506c00d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7234,13 +7234,13 @@ sk_reuseport_is_valid_access(int off, int size,
return size == size_default;
/* Fields that allow narrowing */
- case offsetof(struct sk_reuseport_md, eth_protocol):
+ case bpf_ctx_range(struct sk_reuseport_md, eth_protocol):
if (size < FIELD_SIZEOF(struct sk_buff, protocol))
return false;
/* fall through */
- case offsetof(struct sk_reuseport_md, ip_protocol):
- case offsetof(struct sk_reuseport_md, bind_inany):
- case offsetof(struct sk_reuseport_md, len):
+ case bpf_ctx_range(struct sk_reuseport_md, ip_protocol):
+ case bpf_ctx_range(struct sk_reuseport_md, bind_inany):
+ case bpf_ctx_range(struct sk_reuseport_md, len):
bpf_ctx_record_field_size(info, size_default);
return bpf_ctx_narrow_access_ok(off, size, size_default);
--
2.20.1
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