| Message ID | 20220905143318.1592015-4-roberto.sassu@huaweicloud.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | bpf: Add kfuncs for PKCS#7 signature verification | expand |
On Mon, 5 Sept 2022 at 16:34, Roberto Sassu <roberto.sassu@huaweicloud.com> wrote: > > From: Roberto Sassu <roberto.sassu@huawei.com> > > 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 <joannelkoong@gmail.com> > Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com> > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> > --- Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> > include/linux/bpf_verifier.h | 5 +++++ > include/linux/btf.h | 9 +++++++++ > kernel/bpf/btf.c | 33 +++++++++++++++++++++++++++++++++ > kernel/bpf/verifier.c | 10 +++++----- > 4 files changed, 52 insertions(+), 5 deletions(-) > > diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h > index 1fdddbf3546b..dd58dfccd025 100644 > --- a/include/linux/bpf_verifier.h > +++ b/include/linux/bpf_verifier.h > @@ -571,6 +571,11 @@ 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 ad93c2d9cc1c..f546d368ac5d 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 e49b3b6d48ad..4266bff5fada 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -6362,15 +6362,20 @@ 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", > @@ -6378,6 +6383,34 @@ 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 10b3c0a81d09..8f02729074c6 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -779,8 +779,8 @@ 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); > @@ -799,9 +799,9 @@ 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; > -- > 2.25.1 >
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 1fdddbf3546b..dd58dfccd025 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -571,6 +571,11 @@ 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 ad93c2d9cc1c..f546d368ac5d 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 e49b3b6d48ad..4266bff5fada 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6362,15 +6362,20 @@ 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", @@ -6378,6 +6383,34 @@ 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 10b3c0a81d09..8f02729074c6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -779,8 +779,8 @@ 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); @@ -799,9 +799,9 @@ 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;