Instead of btf_check_subprog_arg_match(), use btf_prepare_func_args()
logic to validate "trustworthiness" of main BPF program's BTF information,
if it is present.
We ignored results of original BTF check anyway, often times producing
confusing and ominously-sounding "reg type unsupported for arg#0
function" message, which has no apparent effect on program correctness
and verification process.
All the -EFAULT returning sanity checks are already performed in
check_btf_info_early(), so there is zero reason to have this duplication
of logic between btf_check_subprog_call() and btf_check_subprog_arg_match().
Dropping btf_check_subprog_arg_match() simplifies
btf_check_func_arg_match() further removing `bool processing_call` flag.
One subtle bit that was done by btf_check_subprog_arg_match() was
potentially marking main program's BTF as unreliable. We do this
explicitly now with a dedicated simple check, preserving the original
behavior, but now based on well factored btf_prepare_func_args() logic.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/linux/bpf.h | 2 -
kernel/bpf/btf.c | 50 ++-----------------
kernel/bpf/verifier.c | 25 +++++-----
.../selftests/bpf/prog_tests/log_fixup.c | 4 +-
.../selftests/bpf/progs/cgrp_kfunc_failure.c | 2 +-
.../selftests/bpf/progs/task_kfunc_failure.c | 2 +-
6 files changed, 19 insertions(+), 66 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6dc82ab156f8..dce11075f83d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2489,8 +2489,6 @@ int btf_distill_func_proto(struct bpf_verifier_log *log,
struct btf_func_model *m);
struct bpf_reg_state;
-int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
- struct bpf_reg_state *regs);
int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
struct bpf_reg_state *regs);
int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index be2104e5f2f5..33d9a1c73f6e 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6768,8 +6768,7 @@ int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *pr
static int btf_check_func_arg_match(struct bpf_verifier_env *env,
const struct btf *btf, u32 func_id,
struct bpf_reg_state *regs,
- bool ptr_to_mem_ok,
- bool processing_call)
+ bool ptr_to_mem_ok)
{
enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
struct bpf_verifier_log *log = &env->log;
@@ -6842,7 +6841,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
i, btf_type_str(t));
return -EINVAL;
}
- } else if (ptr_to_mem_ok && processing_call) {
+ } else if (ptr_to_mem_ok) {
const struct btf_type *resolve_ret;
u32 type_size;
@@ -6867,55 +6866,12 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
return 0;
}
-/* Compare BTF of a function declaration with given bpf_reg_state.
- * Returns:
- * EFAULT - there is a verifier bug. Abort verification.
- * EINVAL - there is a type mismatch or BTF is not available.
- * 0 - BTF matches with what bpf_reg_state expects.
- * Only PTR_TO_CTX and SCALAR_VALUE states are recognized.
- */
-int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
- struct bpf_reg_state *regs)
-{
- struct bpf_prog *prog = env->prog;
- struct btf *btf = prog->aux->btf;
- bool is_global;
- u32 btf_id;
- int err;
-
- if (!prog->aux->func_info)
- return -EINVAL;
-
- btf_id = prog->aux->func_info[subprog].type_id;
- if (!btf_id)
- return -EFAULT;
-
- if (prog->aux->func_info_aux[subprog].unreliable)
- return -EINVAL;
-
- is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
- err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, false);
-
- /* Compiler optimizations can remove arguments from static functions
- * or mismatched type can be passed into a global function.
- * In such cases mark the function as unreliable from BTF point of view.
- */
- if (err)
- prog->aux->func_info_aux[subprog].unreliable = true;
- return err;
-}
-
/* Compare BTF of a function call with given bpf_reg_state.
* Returns:
* EFAULT - there is a verifier bug. Abort verification.
* EINVAL - there is a type mismatch or BTF is not available.
* 0 - BTF matches with what bpf_reg_state expects.
* Only PTR_TO_CTX and SCALAR_VALUE states are recognized.
- *
- * NOTE: the code is duplicated from btf_check_subprog_arg_match()
- * because btf_check_func_arg_match() is still doing both. Once that
- * function is split in 2, we can call from here btf_check_subprog_arg_match()
- * first, and then treat the calling part in a new code path.
*/
int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
struct bpf_reg_state *regs)
@@ -6937,7 +6893,7 @@ int btf_check_subprog_call(struct bpf_verifier_env *env, int subprog,
return -EINVAL;
is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
- err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global, true);
+ err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global);
/* Compiler optimizations can remove arguments from static functions
* or mismatched type can be passed into a global function.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d2436b4749f7..a038d24c6855 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19869,6 +19869,7 @@ static void free_states(struct bpf_verifier_env *env)
static int do_check_common(struct bpf_verifier_env *env, int subprog)
{
bool pop_log = !(env->log.level & BPF_LOG_LEVEL2);
+ struct bpf_subprog_info *sub = subprog_info(env, subprog);
struct bpf_verifier_state *state;
struct bpf_reg_state *regs;
int ret, i;
@@ -19895,9 +19896,9 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
state->first_insn_idx = env->subprog_info[subprog].start;
state->last_insn_idx = -1;
+
regs = state->frame[state->curframe]->regs;
if (subprog || env->prog->type == BPF_PROG_TYPE_EXT) {
- struct bpf_subprog_info *sub = subprog_info(env, subprog);
const char *sub_name = subprog_name(env, subprog);
struct bpf_subprog_arg_info *arg;
struct bpf_reg_state *reg;
@@ -19944,21 +19945,19 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
}
}
} else {
+ /* if main BPF program has associated BTF info, validate that
+ * it's matching expected signature, and otherwise mark BTF
+ * info for main program as unreliable
+ */
+ if (env->prog->aux->func_info_aux) {
+ ret = btf_prepare_func_args(env, 0);
+ if (ret || sub->arg_cnt != 1 || sub->args[0].arg_type != ARG_PTR_TO_CTX)
+ env->prog->aux->func_info_aux[0].unreliable = true;
+ }
+
/* 1st arg to a function */
regs[BPF_REG_1].type = PTR_TO_CTX;
mark_reg_known_zero(env, regs, BPF_REG_1);
- ret = btf_check_subprog_arg_match(env, subprog, regs);
- if (ret == -EFAULT)
- /* unlikely verifier bug. abort.
- * ret == 0 and ret < 0 are sadly acceptable for
- * main() function due to backward compatibility.
- * Like socket filter program may be written as:
- * int bpf_prog(struct pt_regs *ctx)
- * and never dereference that ctx in the program.
- * 'struct pt_regs' is a type mismatch for socket
- * filter that should be using 'struct __sk_buff'.
- */
- goto out;
}
ret = do_check(env);
diff --git a/tools/testing/selftests/bpf/prog_tests/log_fixup.c b/tools/testing/selftests/bpf/prog_tests/log_fixup.c
index effd78b2a657..7a3fa2ff567b 100644
--- a/tools/testing/selftests/bpf/prog_tests/log_fixup.c
+++ b/tools/testing/selftests/bpf/prog_tests/log_fixup.c
@@ -169,9 +169,9 @@ void test_log_fixup(void)
if (test__start_subtest("bad_core_relo_trunc_none"))
bad_core_relo(0, TRUNC_NONE /* full buf */);
if (test__start_subtest("bad_core_relo_trunc_partial"))
- bad_core_relo(300, TRUNC_PARTIAL /* truncate original log a bit */);
+ bad_core_relo(280, TRUNC_PARTIAL /* truncate original log a bit */);
if (test__start_subtest("bad_core_relo_trunc_full"))
- bad_core_relo(210, TRUNC_FULL /* truncate also libbpf's message patch */);
+ bad_core_relo(220, TRUNC_FULL /* truncate also libbpf's message patch */);
if (test__start_subtest("bad_core_relo_subprog"))
bad_core_relo_subprog();
if (test__start_subtest("missing_map"))
diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
index 0fa564a5cc5b..9fe9c4a4e8f6 100644
--- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_failure.c
@@ -78,7 +78,7 @@ int BPF_PROG(cgrp_kfunc_acquire_fp, struct cgroup *cgrp, const char *path)
}
SEC("kretprobe/cgroup_destroy_locked")
-__failure __msg("reg type unsupported for arg#0 function")
+__failure __msg("calling kernel function bpf_cgroup_acquire is not allowed")
int BPF_PROG(cgrp_kfunc_acquire_unsafe_kretprobe, struct cgroup *cgrp)
{
struct cgroup *acquired;
diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
index dcdea3127086..ad88a3796ddf 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
@@ -248,7 +248,7 @@ int BPF_PROG(task_kfunc_from_pid_no_null_check, struct task_struct *task, u64 cl
}
SEC("lsm/task_free")
-__failure __msg("reg type unsupported for arg#0 function")
+__failure __msg("R1 must be a rcu pointer")
int BPF_PROG(task_kfunc_from_lsm_task_free, struct task_struct *task)
{
struct task_struct *acquired;
--
2.34.1
