From: Roberto Sassu Date: Tue, 20 Sep 2022 07:59:42 +0000 (+0200) Subject: btf: Allow dynamic pointer parameters in kfuncs X-Git-Tag: v6.6.17~6504^2~10^2~35^2~9 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b8d31762a0ae6861e1115302ee338560d853e317;p=platform%2Fkernel%2Flinux-rpi.git btf: Allow dynamic pointer parameters in kfuncs Allow dynamic pointers (struct bpf_dynptr_kern *) to be specified as parameters in kfuncs. Also, ensure that dynamic pointers passed as argument are valid and initialized, are a pointer to the stack, and of the type local. More dynamic pointer types can be supported in the future. To properly detect whether a parameter is of the desired type, introduce the stringify_struct() macro to compare the returned structure name with the desired name. In addition, protect against structure renames, by halting the build with BUILD_BUG_ON(), so that developers have to revisit the code. To check if a dynamic pointer passed to the kfunc is valid and initialized, and if its type is local, export the existing functions is_dynptr_reg_valid_init() and is_dynptr_type_expected(). Cc: Joanne Koong Cc: Kumar Kartikeya Dwivedi Signed-off-by: Roberto Sassu Acked-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20220920075951.929132-5-roberto.sassu@huaweicloud.com Signed-off-by: Alexei Starovoitov --- diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index e197f8f..9e1e696 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -593,6 +593,11 @@ int check_kfunc_mem_size_reg(struct bpf_verifier_env *env, struct bpf_reg_state u32 regno); int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg, u32 regno, u32 mem_size); +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, + struct bpf_reg_state *reg); +bool is_dynptr_type_expected(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, + enum bpf_arg_type arg_type); /* this lives here instead of in bpf.h because it needs to dereference tgt_prog */ static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog, diff --git a/include/linux/btf.h b/include/linux/btf.h index 1fcc833..f9aabab 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -52,6 +52,15 @@ #define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */ #define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */ +/* + * Return the name of the passed struct, if exists, or halt the build if for + * example the structure gets renamed. In this way, developers have to revisit + * the code using that structure name, and update it accordingly. + */ +#define stringify_struct(x) \ + ({ BUILD_BUG_ON(sizeof(struct x) < 0); \ + __stringify(x); }) + struct btf; struct btf_member; struct btf_type; diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index dbcf020..13faede 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6449,15 +6449,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, if (is_kfunc) { bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], ®s[regno + 1]); + bool arg_dynptr = btf_type_is_struct(ref_t) && + !strcmp(ref_tname, + stringify_struct(bpf_dynptr_kern)); /* Permit pointer to mem, but only when argument * type is pointer to scalar, or struct composed * (recursively) of scalars. * When arg_mem_size is true, the pointer can be * void *. + * Also permit initialized local dynamic pointers. */ if (!btf_type_is_scalar(ref_t) && !__btf_type_is_scalar_struct(log, btf, ref_t, 0) && + !arg_dynptr && (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) { bpf_log(log, "arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n", @@ -6465,6 +6470,34 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, return -EINVAL; } + if (arg_dynptr) { + if (reg->type != PTR_TO_STACK) { + bpf_log(log, "arg#%d pointer type %s %s not to stack\n", + i, btf_type_str(ref_t), + ref_tname); + return -EINVAL; + } + + if (!is_dynptr_reg_valid_init(env, reg)) { + bpf_log(log, + "arg#%d pointer type %s %s must be valid and initialized\n", + i, btf_type_str(ref_t), + ref_tname); + return -EINVAL; + } + + if (!is_dynptr_type_expected(env, reg, + ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL)) { + bpf_log(log, + "arg#%d pointer type %s %s points to unsupported dynamic pointer type\n", + i, btf_type_str(ref_t), + ref_tname); + return -EINVAL; + } + + continue; + } + /* Check for mem, len pair */ if (arg_mem_size) { if (check_kfunc_mem_size_reg(env, ®s[regno + 1], regno + 1)) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c08dde1..6f6d2d5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -782,8 +782,8 @@ static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env *env, struct bpf_ return true; } -static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, - struct bpf_reg_state *reg) +bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, + struct bpf_reg_state *reg) { struct bpf_func_state *state = func(env, reg); int spi = get_spi(reg->off); @@ -802,9 +802,9 @@ static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, return true; } -static bool is_dynptr_type_expected(struct bpf_verifier_env *env, - struct bpf_reg_state *reg, - enum bpf_arg_type arg_type) +bool is_dynptr_type_expected(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, + enum bpf_arg_type arg_type) { struct bpf_func_state *state = func(env, reg); enum bpf_dynptr_type dynptr_type;