linux-kernel - [PATCH v4 net-next 09/13] selftests/bpf: don't try to access past MAX_PACKET_OFF in test

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Date:   Thu, 3 Aug 2017 17:14:58 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <davem@...emloft.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        iovisor-dev <iovisor-dev@...ts.iovisor.org>
Subject: [PATCH v4 net-next 09/13] selftests/bpf: don't try to access past
 MAX_PACKET_OFF in test_verifier

A number of selftests fell foul of the changed MAX_PACKET_OFF handling.
For instance, "direct packet access: test2" was potentially reading four
 bytes from pkt + 0xffff, which could take it past the verifier's limit,
 causing the program to be rejected (checks against pkt_end didn't give
 us any reg->range).
Increase the shifts by one so that R2 is now mask 0x7fff instead of
 mask 0xffff.

Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 tools/testing/selftests/bpf/test_verifier.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 0691494..876b878 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -2330,8 +2330,8 @@ static struct bpf_test tests[] = {
 				    offsetof(struct __sk_buff, data)),
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_3, BPF_REG_4),
 			BPF_MOV64_REG(BPF_REG_2, BPF_REG_1),
-			BPF_ALU64_IMM(BPF_LSH, BPF_REG_2, 48),
-			BPF_ALU64_IMM(BPF_RSH, BPF_REG_2, 48),
+			BPF_ALU64_IMM(BPF_LSH, BPF_REG_2, 49),
+			BPF_ALU64_IMM(BPF_RSH, BPF_REG_2, 49),
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_3, BPF_REG_2),
 			BPF_MOV64_REG(BPF_REG_2, BPF_REG_3),
 			BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 8),
@@ -2710,11 +2710,11 @@ static struct bpf_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 0xffffffff),
 			BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
 			BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
-			BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffff),
+			BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0x7fff),
 			BPF_MOV64_REG(BPF_REG_4, BPF_REG_0),
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_2),
 			BPF_MOV64_REG(BPF_REG_5, BPF_REG_4),
-			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 0xffff - 1),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 0x7fff - 1),
 			BPF_JMP_REG(BPF_JGT, BPF_REG_4, BPF_REG_3, 1),
 			BPF_STX_MEM(BPF_DW, BPF_REG_5, BPF_REG_4, 0),
 			BPF_MOV64_IMM(BPF_REG_0, 0),
@@ -2736,10 +2736,10 @@ static struct bpf_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_4, 0xffffffff),
 			BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_4, -8),
 			BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8),
-			BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 0xffff),
+			BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 0x7fff),
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_2),
 			BPF_MOV64_REG(BPF_REG_5, BPF_REG_4),
-			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 0xffff - 1),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 0x7fff - 1),
 			BPF_JMP_REG(BPF_JGT, BPF_REG_4, BPF_REG_3, 1),
 			BPF_STX_MEM(BPF_DW, BPF_REG_5, BPF_REG_4, 0),
 			BPF_MOV64_IMM(BPF_REG_0, 0),
@@ -2765,7 +2765,7 @@ static struct bpf_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_4, 0xffffffff),
 			BPF_STX_XADD(BPF_DW, BPF_REG_10, BPF_REG_4, -8),
 			BPF_LDX_MEM(BPF_DW, BPF_REG_4, BPF_REG_10, -8),
-			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 48),
+			BPF_ALU64_IMM(BPF_RSH, BPF_REG_4, 49),
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_2),
 			BPF_MOV64_REG(BPF_REG_0, BPF_REG_4),
 			BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 2),
@@ -2820,7 +2820,7 @@ static struct bpf_test tests[] = {
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_4),
 			BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_2),
 			BPF_MOV64_REG(BPF_REG_5, BPF_REG_0),
-			BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 0xffff - 1),
+			BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 0x7fff - 1),
 			BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 1),
 			BPF_STX_MEM(BPF_DW, BPF_REG_5, BPF_REG_0, 0),
 			BPF_MOV64_IMM(BPF_REG_0, 0),