From cc074822465d18a2d39e0b3e2b48b6766a568db2 Mon Sep 17 00:00:00 2001 From: Hou Tao Date: Sat, 17 Dec 2022 14:21:44 +0800 Subject: bpf: Define sock security related BTF IDs under CONFIG_SECURITY_NETWORK There are warnings reported from resolve_btfids when building vmlinux with CONFIG_SECURITY_NETWORK disabled: WARN: resolve_btfids: unresolved symbol bpf_lsm_sk_free_security WARN: resolve_btfids: unresolved symbol bpf_lsm_sk_alloc_security So only define BTF IDs for these LSM hooks when CONFIG_SECURITY_NETWORK is enabled. Fixes: c0c852dd1876 ("bpf: Do not mark certain LSM hook arguments as trusted") Signed-off-by: Hou Tao Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20221217062144.2507222-1-houtao@huaweicloud.com --- kernel/bpf/bpf_lsm.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel') diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index 9ea42a45da47..a4a41ee3e80b 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -351,8 +351,10 @@ BTF_ID(func, bpf_lsm_bpf_prog_alloc_security) BTF_ID(func, bpf_lsm_bpf_prog_free_security) BTF_ID(func, bpf_lsm_file_alloc_security) BTF_ID(func, bpf_lsm_file_free_security) +#ifdef CONFIG_SECURITY_NETWORK BTF_ID(func, bpf_lsm_sk_alloc_security) BTF_ID(func, bpf_lsm_sk_free_security) +#endif /* CONFIG_SECURITY_NETWORK */ BTF_ID(func, bpf_lsm_task_free) BTF_SET_END(untrusted_lsm_hooks) -- cgit v1.2.3 From 8374bfd5a3c90a5b250f7c087c4d2b8ac467b12e Mon Sep 17 00:00:00 2001 From: Hao Sun Date: Thu, 22 Dec 2022 10:44:13 +0800 Subject: bpf: fix nullness propagation for reg to reg comparisons After befae75856ab, the verifier would propagate null information after JEQ/JNE, e.g., if two pointers, one is maybe_null and the other is not, the former would be marked as non-null in eq path. However, as comment "PTR_TO_BTF_ID points to a kernel struct that does not need to be null checked by the BPF program ... The verifier must keep this in mind and can make no assumptions about null or non-null when doing branch ...". If one pointer is maybe_null and the other is PTR_TO_BTF, the former is incorrectly marked non-null. The following BPF prog can trigger a null-ptr-deref, also see this report for more details[1]: 0: (18) r1 = map_fd ; R1_w=map_ptr(ks=4, vs=4) 2: (79) r6 = *(u64 *)(r1 +8) ; R6_w=bpf_map->inner_map_data ; R6 is PTR_TO_BTF_ID ; equals to null at runtime 3: (bf) r2 = r10 4: (07) r2 += -4 5: (62) *(u32 *)(r2 +0) = 0 6: (85) call bpf_map_lookup_elem#1 ; R0_w=map_value_or_null 7: (1d) if r6 == r0 goto pc+1 8: (95) exit ; from 7 to 9: R0=map_value R6=ptr_bpf_map 9: (61) r0 = *(u32 *)(r0 +0) ; null-ptr-deref 10: (95) exit So, make the verifier propagate nullness information for reg to reg comparisons only if neither reg is PTR_TO_BTF_ID. [1] https://lore.kernel.org/bpf/CACkBjsaFJwjC5oiw-1KXvcazywodwXo4zGYsRHwbr2gSG9WcSw@mail.gmail.com/T/#u Fixes: befae75856ab ("bpf: propagate nullness information for reg to reg comparisons") Signed-off-by: Hao Sun Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20221222024414.29539-1-sunhao.th@gmail.com Signed-off-by: Martin KaFai Lau --- kernel/bpf/verifier.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a5255a0dcbb6..243d06ce6842 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11822,10 +11822,17 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, * register B - not null * for JNE A, B, ... - A is not null in the false branch; * for JEQ A, B, ... - A is not null in the true branch. + * + * Since PTR_TO_BTF_ID points to a kernel struct that does + * not need to be null checked by the BPF program, i.e., + * could be null even without PTR_MAYBE_NULL marking, so + * only propagate nullness when neither reg is that type. */ if (!is_jmp32 && BPF_SRC(insn->code) == BPF_X && __is_pointer_value(false, src_reg) && __is_pointer_value(false, dst_reg) && - type_may_be_null(src_reg->type) != type_may_be_null(dst_reg->type)) { + type_may_be_null(src_reg->type) != type_may_be_null(dst_reg->type) && + base_type(src_reg->type) != PTR_TO_BTF_ID && + base_type(dst_reg->type) != PTR_TO_BTF_ID) { eq_branch_regs = NULL; switch (opcode) { case BPF_JEQ: -- cgit v1.2.3