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eddyz87Alexei Starovoitov
eddyz87
authored and
Alexei Starovoitov
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selftests/bpf: verifier/jeq_infer_not_null converted to inline assembly
Test verifier/jeq_infer_not_null automatically converted to use inline assembly. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20230421174234.2391278-9-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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3 files changed

Lines changed: 215 additions & 174 deletions

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‎tools/testing/selftests/bpf/prog_tests/verifier.c‎

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@@ -29,6 +29,7 @@
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#include "verifier_helper_restricted.skel.h"
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#include "verifier_helper_value_access.skel.h"
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#include "verifier_int_ptr.skel.h"
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#include "verifier_jeq_infer_not_null.skel.h"
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#include "verifier_ld_ind.skel.h"
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#include "verifier_leak_ptr.skel.h"
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#include "verifier_map_ptr.skel.h"
@@ -111,6 +112,7 @@ void test_verifier_helper_packet_access(void) { RUN(verifier_helper_packet_acces
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void test_verifier_helper_restricted(void) { RUN(verifier_helper_restricted); }
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void test_verifier_helper_value_access(void) { RUN(verifier_helper_value_access); }
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void test_verifier_int_ptr(void) { RUN(verifier_int_ptr); }
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void test_verifier_jeq_infer_not_null(void) { RUN(verifier_jeq_infer_not_null); }
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void test_verifier_ld_ind(void) { RUN(verifier_ld_ind); }
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void test_verifier_leak_ptr(void) { RUN(verifier_leak_ptr); }
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void test_verifier_map_ptr(void) { RUN(verifier_map_ptr); }

‎tools/testing/selftests/bpf/progs/verifier_jeq_infer_not_null.c‎

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// SPDX-License-Identifier: GPL-2.0
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/* Converted from tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c */
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include "bpf_misc.h"
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struct {
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__uint(type, BPF_MAP_TYPE_XSKMAP);
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__uint(max_entries, 1);
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__type(key, int);
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__type(value, int);
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} map_xskmap SEC(".maps");
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/* This is equivalent to the following program:
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*
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* r6 = skb->sk;
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* r7 = sk_fullsock(r6);
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* r0 = sk_fullsock(r6);
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* if (r0 == 0) return 0; (a)
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* if (r0 != r7) return 0; (b)
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* *r7->type; (c)
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* return 0;
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*
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* It is safe to dereference r7 at point (c), because of (a) and (b).
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* The test verifies that relation r0 == r7 is propagated from (b) to (c).
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*/
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SEC("cgroup/skb")
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__description("jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JNE false branch")
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__success __failure_unpriv __msg_unpriv("R7 pointer comparison")
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__retval(0)
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__naked void socket_for_jne_false_branch(void)
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{
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asm volatile (" \
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/* r6 = skb->sk; */ \
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r6 = *(u64*)(r1 + %[__sk_buff_sk]); \
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/* if (r6 == 0) return 0; */ \
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if r6 == 0 goto l0_%=; \
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/* r7 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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r7 = r0; \
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/* r0 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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/* if (r0 == null) return 0; */ \
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if r0 == 0 goto l0_%=; \
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/* if (r0 == r7) r0 = *(r7->type); */ \
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if r0 != r7 goto l0_%=; /* Use ! JNE ! */\
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r0 = *(u32*)(r7 + %[bpf_sock_type]); \
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l0_%=: /* return 0 */ \
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r0 = 0; \
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exit; \
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" :
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: __imm(bpf_sk_fullsock),
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__imm_const(__sk_buff_sk, offsetof(struct __sk_buff, sk)),
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__imm_const(bpf_sock_type, offsetof(struct bpf_sock, type))
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: __clobber_all);
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}
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/* Same as above, but verify that another branch of JNE still
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* prohibits access to PTR_MAYBE_NULL.
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*/
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SEC("cgroup/skb")
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__description("jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JNE true branch")
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__failure __msg("R7 invalid mem access 'sock_or_null'")
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__failure_unpriv __msg_unpriv("R7 pointer comparison")
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__naked void unchanged_for_jne_true_branch(void)
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{
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asm volatile (" \
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/* r6 = skb->sk */ \
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r6 = *(u64*)(r1 + %[__sk_buff_sk]); \
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/* if (r6 == 0) return 0; */ \
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if r6 == 0 goto l0_%=; \
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/* r7 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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r7 = r0; \
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/* r0 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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/* if (r0 == null) return 0; */ \
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if r0 != 0 goto l0_%=; \
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/* if (r0 == r7) return 0; */ \
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if r0 != r7 goto l1_%=; /* Use ! JNE ! */\
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goto l0_%=; \
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l1_%=: /* r0 = *(r7->type); */ \
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r0 = *(u32*)(r7 + %[bpf_sock_type]); \
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l0_%=: /* return 0 */ \
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r0 = 0; \
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exit; \
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" :
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: __imm(bpf_sk_fullsock),
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__imm_const(__sk_buff_sk, offsetof(struct __sk_buff, sk)),
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__imm_const(bpf_sock_type, offsetof(struct bpf_sock, type))
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: __clobber_all);
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}
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/* Same as a first test, but not null should be inferred for JEQ branch */
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SEC("cgroup/skb")
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__description("jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JEQ true branch")
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__success __failure_unpriv __msg_unpriv("R7 pointer comparison")
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__retval(0)
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__naked void socket_for_jeq_true_branch(void)
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{
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asm volatile (" \
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/* r6 = skb->sk; */ \
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r6 = *(u64*)(r1 + %[__sk_buff_sk]); \
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/* if (r6 == null) return 0; */ \
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if r6 == 0 goto l0_%=; \
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/* r7 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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r7 = r0; \
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/* r0 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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/* if (r0 == null) return 0; */ \
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if r0 == 0 goto l0_%=; \
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/* if (r0 != r7) return 0; */ \
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if r0 == r7 goto l1_%=; /* Use ! JEQ ! */\
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goto l0_%=; \
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l1_%=: /* r0 = *(r7->type); */ \
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r0 = *(u32*)(r7 + %[bpf_sock_type]); \
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l0_%=: /* return 0; */ \
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r0 = 0; \
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exit; \
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" :
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: __imm(bpf_sk_fullsock),
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__imm_const(__sk_buff_sk, offsetof(struct __sk_buff, sk)),
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__imm_const(bpf_sock_type, offsetof(struct bpf_sock, type))
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: __clobber_all);
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}
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/* Same as above, but verify that another branch of JNE still
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* prohibits access to PTR_MAYBE_NULL.
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*/
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SEC("cgroup/skb")
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__description("jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JEQ false branch")
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__failure __msg("R7 invalid mem access 'sock_or_null'")
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__failure_unpriv __msg_unpriv("R7 pointer comparison")
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__naked void unchanged_for_jeq_false_branch(void)
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{
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asm volatile (" \
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/* r6 = skb->sk; */ \
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r6 = *(u64*)(r1 + %[__sk_buff_sk]); \
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/* if (r6 == null) return 0; */ \
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if r6 == 0 goto l0_%=; \
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/* r7 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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r7 = r0; \
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/* r0 = sk_fullsock(skb); */ \
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r1 = r6; \
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call %[bpf_sk_fullsock]; \
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/* if (r0 == null) return 0; */ \
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if r0 == 0 goto l0_%=; \
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/* if (r0 != r7) r0 = *(r7->type); */ \
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if r0 == r7 goto l0_%=; /* Use ! JEQ ! */\
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r0 = *(u32*)(r7 + %[bpf_sock_type]); \
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l0_%=: /* return 0; */ \
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r0 = 0; \
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exit; \
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" :
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: __imm(bpf_sk_fullsock),
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__imm_const(__sk_buff_sk, offsetof(struct __sk_buff, sk)),
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__imm_const(bpf_sock_type, offsetof(struct bpf_sock, type))
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: __clobber_all);
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}
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/* Maps are treated in a different branch of `mark_ptr_not_null_reg`,
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* so separate test for maps case.
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*/
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SEC("xdp")
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__description("jne/jeq infer not null, PTR_TO_MAP_VALUE_OR_NULL -> PTR_TO_MAP_VALUE")
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__success __retval(0)
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__naked void null_ptr_to_map_value(void)
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{
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asm volatile (" \
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/* r9 = &some stack to use as key */ \
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r1 = 0; \
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*(u32*)(r10 - 8) = r1; \
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r9 = r10; \
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r9 += -8; \
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/* r8 = process local map */ \
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r8 = %[map_xskmap] ll; \
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/* r6 = map_lookup_elem(r8, r9); */ \
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r1 = r8; \
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r2 = r9; \
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call %[bpf_map_lookup_elem]; \
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r6 = r0; \
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/* r7 = map_lookup_elem(r8, r9); */ \
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r1 = r8; \
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r2 = r9; \
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call %[bpf_map_lookup_elem]; \
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r7 = r0; \
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/* if (r6 == 0) return 0; */ \
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if r6 == 0 goto l0_%=; \
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/* if (r6 != r7) return 0; */ \
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if r6 != r7 goto l0_%=; \
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/* read *r7; */ \
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r0 = *(u32*)(r7 + %[bpf_xdp_sock_queue_id]); \
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l0_%=: /* return 0; */ \
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r0 = 0; \
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exit; \
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" :
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: __imm(bpf_map_lookup_elem),
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__imm_addr(map_xskmap),
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__imm_const(bpf_xdp_sock_queue_id, offsetof(struct bpf_xdp_sock, queue_id))
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: __clobber_all);
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}
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char _license[] SEC("license") = "GPL";

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