From: Frank van der Linden <fllinden@amazon.com>
To: <stable@vger.kernel.org>
Cc: <bpf@vger.kernel.org>, <ast@kernel.org>, <daniel@iogearbox.net>,
<yhs@fb.com>, <john.fastabend@gmail.com>, <samjonas@amazon.com>
Subject: [PATCH 4.14 15/15] selftests/bpf: make 'dubious pointer arithmetic' test useful
Date: Sat, 1 May 2021 04:30:14 +0000 [thread overview]
Message-ID: <20210501043014.33300-16-fllinden@amazon.com> (raw)
In-Reply-To: <20210501043014.33300-1-fllinden@amazon.com>
From: Alexei Starovoitov <ast@kernel.org>
Upstream commit 31e95b61e172144bb2b626a291db1bdc0769275b
mostly revert the previous workaround and make
'dubious pointer arithmetic' test useful again.
Use (ptr - ptr) << const instead of ptr << const to generate large scalar.
The rest stays as before commit 2b36047e7889.
Fixes: 2b36047e7889 ("selftests/bpf: fix test_align")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
[fllinden@amazon.com: adjust for 4.14 (no liveness of regs in output)]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
---
tools/testing/selftests/bpf/test_align.c | 30 ++++++++++++++++++------
1 file changed, 23 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_align.c b/tools/testing/selftests/bpf/test_align.c
index 471bbbdb94db..5d530c90779e 100644
--- a/tools/testing/selftests/bpf/test_align.c
+++ b/tools/testing/selftests/bpf/test_align.c
@@ -446,11 +446,9 @@ static struct bpf_align_test tests[] = {
.insns = {
PREP_PKT_POINTERS,
BPF_MOV64_IMM(BPF_REG_0, 0),
- /* ptr & const => unknown & const */
- BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
- BPF_ALU64_IMM(BPF_AND, BPF_REG_5, 0x40),
- /* ptr << const => unknown << const */
- BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
+ /* (ptr - ptr) << 2 */
+ BPF_MOV64_REG(BPF_REG_5, BPF_REG_3),
+ BPF_ALU64_REG(BPF_SUB, BPF_REG_5, BPF_REG_2),
BPF_ALU64_IMM(BPF_LSH, BPF_REG_5, 2),
/* We have a (4n) value. Let's make a packet offset
* out of it. First add 14, to make it a (4n+2)
@@ -473,8 +471,26 @@ static struct bpf_align_test tests[] = {
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.result = REJECT,
.matches = {
- {4, "R5=pkt(id=0,off=0,r=0,imm=0)"},
- /* R5 bitwise operator &= on pointer prohibited */
+ {4, "R5=pkt_end(id=0,off=0,imm=0)"},
+ /* (ptr - ptr) << 2 == unknown, (4n) */
+ {6, "R5=inv(id=0,smax_value=9223372036854775804,umax_value=18446744073709551612,var_off=(0x0; 0xfffffffffffffffc))"},
+ /* (4n) + 14 == (4n+2). We blow our bounds, because
+ * the add could overflow.
+ */
+ {7, "R5=inv(id=0,var_off=(0x2; 0xfffffffffffffffc))"},
+ /* Checked s>=0 */
+ {9, "R5=inv(id=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ /* packet pointer + nonnegative (4n+2) */
+ {11, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ {13, "R4=pkt(id=1,off=4,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
+ /* NET_IP_ALIGN + (4n+2) == (4n), alignment is fine.
+ * We checked the bounds, but it might have been able
+ * to overflow if the packet pointer started in the
+ * upper half of the address space.
+ * So we did not get a 'range' on R6, and the access
+ * attempt will fail.
+ */
+ {15, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
}
},
{
--
2.23.3
prev parent reply other threads:[~2021-05-01 4:31 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-01 4:29 [PATCH 4.14 00/15] fix backports, add CVE-2021-29155 fixes Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 01/15] bpf: Fix backport of "bpf: restrict unknown scalars of mixed signed bounds for unprivileged" Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 02/15] bpf: fix up selftests after backports were fixed Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 03/15] bpf, selftests: Fix up some test_verifier cases for unprivileged Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 04/15] bpf: Move off_reg into sanitize_ptr_alu Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 05/15] bpf: Ensure off_reg has no mixed signed bounds for all types Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 06/15] bpf: Rework ptr_limit into alu_limit and add common error path Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 07/15] bpf: Improve verifier error messages for users Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 08/15] bpf: Refactor and streamline bounds check into helper Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 09/15] bpf: Move sanitize_val_alu out of op switch Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 10/15] bpf: Tighten speculative pointer arithmetic mask Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 11/15] bpf: Update selftests to reflect new error states Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 12/15] bpf: do not allow root to mangle valid pointers Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 13/15] bpf/verifier: disallow pointer subtraction Frank van der Linden
2021-05-01 4:30 ` [PATCH 4.14 14/15] selftests/bpf: fix test_align Frank van der Linden
2021-05-01 4:30 ` Frank van der Linden [this message]
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