kernel / kernel-source

Clone
Source Code
GIT

Files

  1.   678063aa1425c5fee2dc993e6cd635f549601f8b
  2.   patches.suse
  3.   bpf-selftests-Add-test-case-for-atomic-fetch-on-spil.patch
Blob Blame History Raw 
From: Daniel Borkmann <daniel@iogearbox.net>
Date: Tue, 7 Dec 2021 10:07:04 +0000
Subject: bpf, selftests: Add test case for atomic fetch on spilled pointer
Patch-mainline: v5.16-rc6
Git-commit: 180486b430f4e22cc00a478163d942804baae4b5
References: git-fixes bsc#1193883 bsc#1194826 CVE-2022-0264
X-Info: dependency of "bpf, selftests: Update test case for atomic cmpxchg on r0 with pointer" e523102cb719cbad1673b6aa2a4d5c1fa6f13799

Test whether unprivileged would be able to leak the spilled pointer either
by exporting the returned value from the atomic{32,64} operation or by reading
and exporting the value from the stack after the atomic operation took place.

Note that for unprivileged, the below atomic cmpxchg test case named "Dest
pointer in r0 - succeed" is failing. The reason is that in the dst memory
location (r10 -8) there is the spilled register r10:

  0: R1=ctx(id=0,off=0,imm=0) R10=fp0
  0: (bf) r0 = r10
  1: R0_w=fp0 R1=ctx(id=0,off=0,imm=0) R10=fp0
  1: (7b) *(u64 *)(r10 -8) = r0
  2: R0_w=fp0 R1=ctx(id=0,off=0,imm=0) R10=fp0 fp-8_w=fp
  2: (b7) r1 = 0
  3: R0_w=fp0 R1_w=invP0 R10=fp0 fp-8_w=fp
  3: (db) r0 = atomic64_cmpxchg((u64 *)(r10 -8), r0, r1)
  4: R0_w=fp0 R1_w=invP0 R10=fp0 fp-8_w=mmmmmmmm
  4: (79) r1 = *(u64 *)(r0 -8)
  5: R0_w=fp0 R1_w=invP(id=0) R10=fp0 fp-8_w=mmmmmmmm
  5: (b7) r0 = 0
  6: R0_w=invP0 R1_w=invP(id=0) R10=fp0 fp-8_w=mmmmmmmm
  6: (95) exit

However, allowing this case for unprivileged is a bit useless given an
update with a new pointer will fail anyway:

  0: R1=ctx(id=0,off=0,imm=0) R10=fp0
  0: (bf) r0 = r10
  1: R0_w=fp0 R1=ctx(id=0,off=0,imm=0) R10=fp0
  1: (7b) *(u64 *)(r10 -8) = r0
  2: R0_w=fp0 R1=ctx(id=0,off=0,imm=0) R10=fp0 fp-8_w=fp
  2: (db) r0 = atomic64_cmpxchg((u64 *)(r10 -8), r0, r10)
  R10 leaks addr into mem

Acked-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/testing/selftests/bpf/verifier/atomic_cmpxchg.c |   23 ++++
 tools/testing/selftests/bpf/verifier/atomic_fetch.c   |   94 ++++++++++++++++++
 2 files changed, 117 insertions(+)

--- a/tools/testing/selftests/bpf/verifier/atomic_cmpxchg.c
+++ b/tools/testing/selftests/bpf/verifier/atomic_cmpxchg.c
@@ -156,4 +156,27 @@
 		BPF_EXIT_INSN(),
 	},
 	.result = ACCEPT,
+	.result_unpriv = REJECT,
+	.errstr_unpriv = "leaking pointer from stack off -8",
+},
+{
+	"Dest pointer in r0 - succeed, check 2",
+	.insns = {
+		/* r0 = &val */
+		BPF_MOV64_REG(BPF_REG_0, BPF_REG_10),
+		/* val = r0; */
+		BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
+		/* r5 = &val */
+		BPF_MOV64_REG(BPF_REG_5, BPF_REG_10),
+		/* r0 = atomic_cmpxchg(&val, r0, r5); */
+		BPF_ATOMIC_OP(BPF_DW, BPF_CMPXCHG, BPF_REG_10, BPF_REG_5, -8),
+		/* r1 = *r0 */
+		BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, -8),
+		/* exit(0); */
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.result_unpriv = REJECT,
+	.errstr_unpriv = "R5 leaks addr into mem",
 },
--- a/tools/testing/selftests/bpf/verifier/atomic_fetch.c
+++ b/tools/testing/selftests/bpf/verifier/atomic_fetch.c
@@ -1,3 +1,97 @@
+{
+	"atomic dw/fetch and address leakage of (map ptr & -1) via stack slot",
+	.insns = {
+		BPF_LD_IMM64(BPF_REG_1, -1),
+		BPF_LD_MAP_FD(BPF_REG_8, 0),
+		BPF_LD_MAP_FD(BPF_REG_9, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_9, 0),
+		BPF_ATOMIC_OP(BPF_DW, BPF_AND | BPF_FETCH, BPF_REG_2, BPF_REG_1, 0),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_2, 0),
+		BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+		BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_9, 0),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.fixup_map_array_48b = { 2, 4 },
+	.result = ACCEPT,
+	.result_unpriv = REJECT,
+	.errstr_unpriv = "leaking pointer from stack off -8",
+},
+{
+	"atomic dw/fetch and address leakage of (map ptr & -1) via returned value",
+	.insns = {
+		BPF_LD_IMM64(BPF_REG_1, -1),
+		BPF_LD_MAP_FD(BPF_REG_8, 0),
+		BPF_LD_MAP_FD(BPF_REG_9, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_9, 0),
+		BPF_ATOMIC_OP(BPF_DW, BPF_AND | BPF_FETCH, BPF_REG_2, BPF_REG_1, 0),
+		BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),
+		BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+		BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_9, 0),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.fixup_map_array_48b = { 2, 4 },
+	.result = ACCEPT,
+	.result_unpriv = REJECT,
+	.errstr_unpriv = "leaking pointer from stack off -8",
+},
+{
+	"atomic w/fetch and address leakage of (map ptr & -1) via stack slot",
+	.insns = {
+		BPF_LD_IMM64(BPF_REG_1, -1),
+		BPF_LD_MAP_FD(BPF_REG_8, 0),
+		BPF_LD_MAP_FD(BPF_REG_9, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_9, 0),
+		BPF_ATOMIC_OP(BPF_W, BPF_AND | BPF_FETCH, BPF_REG_2, BPF_REG_1, 0),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_9, BPF_REG_2, 0),
+		BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+		BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_9, 0),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.fixup_map_array_48b = { 2, 4 },
+	.result = REJECT,
+	.errstr = "invalid size of register fill",
+},
+{
+	"atomic w/fetch and address leakage of (map ptr & -1) via returned value",
+	.insns = {
+		BPF_LD_IMM64(BPF_REG_1, -1),
+		BPF_LD_MAP_FD(BPF_REG_8, 0),
+		BPF_LD_MAP_FD(BPF_REG_9, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_9, 0),
+		BPF_ATOMIC_OP(BPF_W, BPF_AND | BPF_FETCH, BPF_REG_2, BPF_REG_1, 0),
+		BPF_MOV64_REG(BPF_REG_9, BPF_REG_1),
+		BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+		BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
+		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+		BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_9, 0),
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	},
+	.fixup_map_array_48b = { 2, 4 },
+	.result = REJECT,
+	.errstr = "invalid size of register fill",
+},
 #define __ATOMIC_FETCH_OP_TEST(src_reg, dst_reg, operand1, op, operand2, expect) \
 	{								\
 		"atomic fetch " #op ", src=" #dst_reg " dst=" #dst_reg,	\
Powered by Pagure 5.13.3
Documentation • About this Instance • SSH Hostkey/Fingerprint
© Red Hat, Inc. and others.