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Message-Id: <20230420124455.31099-8-fw@strlen.de>
Date: Thu, 20 Apr 2023 14:44:55 +0200
From: Florian Westphal <fw@...len.de>
To: <bpf@...r.kernel.org>
Cc: netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
dxu@...uu.xyz, qde@...cy.de, Florian Westphal <fw@...len.de>
Subject: [PATCH bpf-next v4 7/7] selftests/bpf: add missing netfilter return value and ctx access tests
Extend prog_tests with two test cases:
# ./test_progs --allow=verifier_netfilter_retcode
#278/1 verifier_netfilter_retcode/bpf_exit with invalid return code. test1:OK
#278/2 verifier_netfilter_retcode/bpf_exit with valid return code. test2:OK
#278/3 verifier_netfilter_retcode/bpf_exit with valid return code. test3:OK
#278/4 verifier_netfilter_retcode/bpf_exit with invalid return code. test4:OK
#278 verifier_netfilter_retcode:OK
This checks that only accept and drop (0,1) are permitted.
NF_QUEUE could be implemented later if we can guarantee that attachment
of such programs can be rejected if they get attached to a pf/hook that
doesn't support async reinjection.
NF_STOLEN could be implemented via trusted helpers that can guarantee
that the skb will eventually be free'd.
v4: test case for bpf_nf_ctx access checks, requested by Alexei Starovoitov.
# ./test_progs --allow=verifier_netfilter_ctx
#280/1 verifier_netfilter_ctx/netfilter invalid context access, size too short:OK
#280/2 verifier_netfilter_ctx/netfilter invalid context access, size too short:OK
#280/3 verifier_netfilter_ctx/netfilter invalid context access, past end of ctx:OK
#280/4 verifier_netfilter_ctx/netfilter invalid context, write:OK
#280/5 verifier_netfilter_ctx/netfilter valid context access:OK
#280/6 verifier_netfilter_ctx/netfilter valid context access @unpriv:OK
#280 verifier_netfilter_ctx:OK
Summary: 1/6 PASSED, 0 SKIPPED, 0 FAILED
This checks:
1/2: partial reads of ctx->{skb,state} are rejected
3. read access past sizeof(ctx) is rejected
4. write to ctx content, e.g. 'ctx->skb = NULL;' is rejected
5. ctx->skb and ctx->state can be read (valid case), but ...
6. ... same program fails for unpriv (CAP_NET_ADMIN needed).
Link: https://lore.kernel.org/bpf/20230419021152.sjq4gttphzzy6b5f@dhcp-172-26-102-232.dhcp.thefacebook.com/
Signed-off-by: Florian Westphal <fw@...len.de>
---
.../selftests/bpf/prog_tests/verifier.c | 4 +
.../bpf/progs/verifier_netfilter_ctx.c | 82 +++++++++++++++++++
.../bpf/progs/verifier_netfilter_retcode.c | 49 +++++++++++
3 files changed, 135 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/verifier_netfilter_ctx.c
create mode 100644 tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c
diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 25bc8958dbfe..2b4ded63ce9f 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -29,6 +29,8 @@
#include "verifier_map_ret_val.skel.h"
#include "verifier_masking.skel.h"
#include "verifier_meta_access.skel.h"
+#include "verifier_netfilter_ctx.skel.h"
+#include "verifier_netfilter_retcode.skel.h"
#include "verifier_raw_stack.skel.h"
#include "verifier_raw_tp_writable.skel.h"
#include "verifier_reg_equal.skel.h"
@@ -94,6 +96,8 @@ void test_verifier_map_ptr(void) { RUN(verifier_map_ptr); }
void test_verifier_map_ret_val(void) { RUN(verifier_map_ret_val); }
void test_verifier_masking(void) { RUN(verifier_masking); }
void test_verifier_meta_access(void) { RUN(verifier_meta_access); }
+void test_verifier_netfilter_ctx(void) { RUN(verifier_netfilter_ctx); }
+void test_verifier_netfilter_retcode(void) { RUN(verifier_netfilter_retcode); }
void test_verifier_raw_stack(void) { RUN(verifier_raw_stack); }
void test_verifier_raw_tp_writable(void) { RUN(verifier_raw_tp_writable); }
void test_verifier_reg_equal(void) { RUN(verifier_reg_equal); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_netfilter_ctx.c b/tools/testing/selftests/bpf/progs/verifier_netfilter_ctx.c
new file mode 100644
index 000000000000..861b2266179f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_netfilter_ctx.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+
+#include "bpf_misc.h"
+
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("netfilter")
+__description("netfilter invalid context access, size too short")
+__failure __msg("invalid bpf_context access")
+__naked void with_invalid_ctx_access_test1(void)
+{
+ asm volatile (" \
+ r2 = *(u8*)(r1 + %[__bpf_nf_ctx_state]); \
+ r0 = 0; \
+ exit; \
+" :
+ : __imm_const(__bpf_nf_ctx_state, offsetof(struct bpf_nf_ctx, state))
+ : __clobber_all);
+}
+
+SEC("netfilter")
+__description("netfilter invalid context access, size too short")
+__failure __msg("invalid bpf_context access")
+__naked void with_invalid_ctx_access_test2(void)
+{
+ asm volatile (" \
+ r2 = *(u16*)(r1 + %[__bpf_nf_ctx_skb]); \
+ r0 = 0; \
+ exit; \
+" :
+ : __imm_const(__bpf_nf_ctx_skb, offsetof(struct bpf_nf_ctx, skb))
+ : __clobber_all);
+}
+
+SEC("netfilter")
+__description("netfilter invalid context access, past end of ctx")
+__failure __msg("invalid bpf_context access")
+__naked void with_invalid_ctx_access_test3(void)
+{
+ asm volatile (" \
+ r2 = *(u64*)(r1 + %[__bpf_nf_ctx_size]); \
+ r0 = 0; \
+ exit; \
+" :
+ : __imm_const(__bpf_nf_ctx_size, sizeof(struct bpf_nf_ctx))
+ : __clobber_all);
+}
+
+SEC("netfilter")
+__description("netfilter invalid context, write")
+__failure __msg("invalid bpf_context access")
+__naked void with_invalid_ctx_access_test4(void)
+{
+ asm volatile (" \
+ r2 = r1; \
+ *(u64*)(r2 + 0) = r1; \
+ r0 = 1; \
+ exit; \
+" :
+ : __imm_const(__bpf_nf_ctx_skb, offsetof(struct bpf_nf_ctx, skb))
+ : __clobber_all);
+}
+
+SEC("netfilter")
+__description("netfilter valid context access")
+__success __failure_unpriv
+__retval(1)
+__naked void with_invalid_ctx_access_test5(void)
+{
+ asm volatile (" \
+ r2 = *(u64*)(r1 + %[__bpf_nf_ctx_state]); \
+ r1 = *(u64*)(r1 + %[__bpf_nf_ctx_skb]); \
+ r0 = 1; \
+ exit; \
+" :
+ : __imm_const(__bpf_nf_ctx_state, offsetof(struct bpf_nf_ctx, state)),
+ __imm_const(__bpf_nf_ctx_skb, offsetof(struct bpf_nf_ctx, skb))
+ : __clobber_all);
+}
diff --git a/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c b/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c
new file mode 100644
index 000000000000..353ae6da00e1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_netfilter_retcode.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+SEC("netfilter")
+__description("bpf_exit with invalid return code. test1")
+__failure __msg("R0 is not a known value")
+__naked void with_invalid_return_code_test1(void)
+{
+ asm volatile (" \
+ r0 = *(u64*)(r1 + 0); \
+ exit; \
+" ::: __clobber_all);
+}
+
+SEC("netfilter")
+__description("bpf_exit with valid return code. test2")
+__success
+__naked void with_valid_return_code_test2(void)
+{
+ asm volatile (" \
+ r0 = 0; \
+ exit; \
+" ::: __clobber_all);
+}
+
+SEC("netfilter")
+__description("bpf_exit with valid return code. test3")
+__success
+__naked void with_valid_return_code_test3(void)
+{
+ asm volatile (" \
+ r0 = 1; \
+ exit; \
+" ::: __clobber_all);
+}
+
+SEC("netfilter")
+__description("bpf_exit with invalid return code. test4")
+__failure __msg("R0 has value (0x2; 0x0)")
+__naked void with_invalid_return_code_test4(void)
+{
+ asm volatile (" \
+ r0 = 2; \
+ exit; \
+" ::: __clobber_all);
+}
--
2.39.2
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