Re: [PATCH bpf-next v7 1/3] bpf: Allow trusted pointers to be passed to KF_TRUSTED_ARGS kfuncs
From: Alexei Starovoitov
Date: Thu Nov 17 2022 - 21:26:55 EST
On Wed, Nov 16, 2022 at 09:24:00PM -0600, David Vernet wrote:
> Kfuncs currently support specifying the KF_TRUSTED_ARGS flag to signal
> to the verifier that it should enforce that a BPF program passes it a
> "safe", trusted pointer. Currently, "safe" means that the pointer is
> either PTR_TO_CTX, or is refcounted. There may be cases, however, where
> the kernel passes a BPF program a safe / trusted pointer to an object
> that the BPF program wishes to use as a kptr, but because the object
> does not yet have a ref_obj_id from the perspective of the verifier, the
> program would be unable to pass it to a KF_ACQUIRE | KF_TRUSTED_ARGS
> kfunc.
>
> The solution is to expand the set of pointers that are considered
> trusted according to KF_TRUSTED_ARGS, so that programs can invoke kfuncs
> with these pointers without getting rejected by the verifier.
>
> There is already a PTR_UNTRUSTED flag that is set in some scenarios,
> such as when a BPF program reads a kptr directly from a map
> without performing a bpf_kptr_xchg() call. These pointers of course can
> and should be rejected by the verifier. Unfortunately, however,
> PTR_UNTRUSTED does not cover all the cases for safety that need to
> be addressed to adequately protect kfuncs. Specifically, pointers
> obtained by a BPF program "walking" a struct are _not_ considered
> PTR_UNTRUSTED according to BPF. For example, say that we were to add a
> kfunc called bpf_task_acquire(), with KF_ACQUIRE | KF_TRUSTED_ARGS, to
> acquire a struct task_struct *. If we only used PTR_UNTRUSTED to signal
> that a task was unsafe to pass to a kfunc, the verifier would mistakenly
> allow the following unsafe BPF program to be loaded:
>
> SEC("tp_btf/task_newtask")
> int BPF_PROG(unsafe_acquire_task,
> struct task_struct *task,
> u64 clone_flags)
> {
> struct task_struct *acquired, *nested;
>
> nested = task->last_wakee;
>
> /* Would not be rejected by the verifier. */
> acquired = bpf_task_acquire(nested);
> if (!acquired)
> return 0;
>
> bpf_task_release(acquired);
> return 0;
> }
>
> To address this, this patch defines a new type flag called PTR_TRUSTED
> which tracks whether a PTR_TO_BTF_ID pointer is safe to pass to a
> KF_TRUSTED_ARGS kfunc or a BPF helper function. PTR_TRUSTED pointers are
> passed directly from the kernel as a tracepoint or struct_ops callback
> argument. Any nested pointer that is obtained from walking a PTR_TRUSTED
> pointer is no longer PTR_TRUSTED. From the example above, the struct
> task_struct *task argument is PTR_TRUSTED, but the 'nested' pointer
> obtained from 'task->last_wakee' is not PTR_TRUSTED.
>
> A subsequent patch will add kfuncs for storing a task kfunc as a kptr,
> and then another patch will add selftests to validate.
>
> Signed-off-by: David Vernet <void@xxxxxxxxxxxxx>
> ---
> Documentation/bpf/kfuncs.rst | 30 ++++-----
> include/linux/bpf.h | 30 +++++++++
> include/linux/btf.h | 65 ++++++++++++-------
> kernel/bpf/btf.c | 38 +++++++++--
> kernel/bpf/verifier.c | 45 ++++++++-----
> kernel/trace/bpf_trace.c | 2 +-
> net/ipv4/bpf_tcp_ca.c | 4 +-
> tools/testing/selftests/bpf/verifier/calls.c | 2 +-
> .../selftests/bpf/verifier/ref_tracking.c | 4 +-
> 9 files changed, 154 insertions(+), 66 deletions(-)
>
> diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
> index 0f858156371d..67b7e2f46ec6 100644
> --- a/Documentation/bpf/kfuncs.rst
> +++ b/Documentation/bpf/kfuncs.rst
> @@ -137,22 +137,20 @@ KF_ACQUIRE and KF_RET_NULL flags.
> --------------------------
>
> The KF_TRUSTED_ARGS flag is used for kfuncs taking pointer arguments. It
> -indicates that the all pointer arguments will always have a guaranteed lifetime,
> -and pointers to kernel objects are always passed to helpers in their unmodified
> -form (as obtained from acquire kfuncs).
> -
> -It can be used to enforce that a pointer to a refcounted object acquired from a
> -kfunc or BPF helper is passed as an argument to this kfunc without any
> -modifications (e.g. pointer arithmetic) such that it is trusted and points to
> -the original object.
> -
> -Meanwhile, it is also allowed pass pointers to normal memory to such kfuncs,
> -but those can have a non-zero offset.
> -
> -This flag is often used for kfuncs that operate (change some property, perform
> -some operation) on an object that was obtained using an acquire kfunc. Such
> -kfuncs need an unchanged pointer to ensure the integrity of the operation being
> -performed on the expected object.
> +indicates that the all pointer arguments are valid, and that all pointers to
> +BTF objects have been passed in their unmodified form (that is, at a zero
> +offset, and without having been obtained from walking another pointer).
> +
> +There are two types of pointers to kernel objects which are considered "valid":
> +
> +1. Pointers which are passed as tracepoint or struct_ops callback arguments.
> +2. Pointers which were returned from a KF_ACQUIRE or KF_KPTR_GET kfunc.
> +
> +Pointers to non-BTF objects (e.g. scalar pointers) may also be passed to
> +KF_TRUSTED_ARGS kfuncs, and may have a non-zero offset.
> +
> +The definition of "valid" pointers is subject to change at any time, and has
> +absolutely no ABI stability guarantees.
>
> 2.4.6 KF_SLEEPABLE flag
> -----------------------
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 54462dd28824..763ae250693e 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -524,6 +524,35 @@ enum bpf_type_flag {
> /* Size is known at compile time. */
> MEM_FIXED_SIZE = BIT(10 + BPF_BASE_TYPE_BITS),
>
> + /* PTR was passed from the kernel in a trusted context, and may be
> + * passed to KF_TRUSTED_ARGS kfuncs or BPF helper functions.
> + * Confusingly, this is _not_ the opposite of PTR_UNTRUSTED above.
> + * PTR_UNTRUSTED refers to a kptr that was read directly from a map
> + * without invoking bpf_kptr_xchg(). What we really need to know is
> + * whether a pointer is safe to pass to a kfunc or BPF helper function.
> + * While PTR_UNTRUSTED pointers are unsafe to pass to kfuncs and BPF
> + * helpers, they do not cover all possible instances of unsafe
> + * pointers. For example, a pointer that was obtained from walking a
> + * struct will _not_ get the PTR_UNTRUSTED type modifier, despite the
> + * fact that it may be NULL, invalid, etc. This is due to backwards
> + * compatibility requirements, as this was the behavior that was first
> + * introduced when kptrs were added. The behavior is now considered
> + * deprecated, and PTR_UNTRUSTED will eventually be removed.
> + *
> + * PTR_TRUSTED, on the other hand, is a pointer that the kernel
> + * guarantees to be valid and safe to pass to kfuncs and BPF helpers.
> + * For example, pointers passed to tracepoint arguments are considered
> + * PTR_TRUSTED, as are pointers that are passed to struct_ops
> + * callbacks. As alluded to above, pointers that are obtained from
> + * walking PTR_TRUSTED pointers are _not_ trusted. For example, if a
> + * struct task_struct *task is PTR_TRUSTED, then accessing
> + * task->last_wakee will lose the PTR_TRUSTED modifier when it's stored
> + * in a BPF register. Similarly, pointers passed to certain programs
> + * types such as kretprobes are not guaranteed to be valid, as they may
> + * for example contain an object that was recently freed.
> + */
> + PTR_TRUSTED = BIT(11 + BPF_BASE_TYPE_BITS),
> +
> __BPF_TYPE_FLAG_MAX,
> __BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1,
> };
> @@ -617,6 +646,7 @@ enum bpf_return_type {
> RET_PTR_TO_RINGBUF_MEM_OR_NULL = PTR_MAYBE_NULL | MEM_RINGBUF | RET_PTR_TO_MEM,
> RET_PTR_TO_DYNPTR_MEM_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_MEM,
> RET_PTR_TO_BTF_ID_OR_NULL = PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
> + RET_PTR_TO_BTF_ID_TRUSTED = PTR_TRUSTED | RET_PTR_TO_BTF_ID,
>
> /* This must be the last entry. Its purpose is to ensure the enum is
> * wide enough to hold the higher bits reserved for bpf_type_flag.
> diff --git a/include/linux/btf.h b/include/linux/btf.h
> index d80345fa566b..13b969e74d3b 100644
> --- a/include/linux/btf.h
> +++ b/include/linux/btf.h
> @@ -17,36 +17,53 @@
> #define KF_RELEASE (1 << 1) /* kfunc is a release function */
> #define KF_RET_NULL (1 << 2) /* kfunc returns a pointer that may be NULL */
> #define KF_KPTR_GET (1 << 3) /* kfunc returns reference to a kptr */
> -/* Trusted arguments are those which are meant to be referenced arguments with
> - * unchanged offset. It is used to enforce that pointers obtained from acquire
> - * kfuncs remain unmodified when being passed to helpers taking trusted args.
> +/* Trusted arguments are those which are guaranteed to be valid when passed to
> + * the kfunc. It is used to enforce that pointers obtained from either acquire
> + * kfuncs, or from the main kernel on a tracepoint or struct_ops callback
> + * invocation, remain unmodified when being passed to helpers taking trusted
> + * args.
> *
> - * Consider
> - * struct foo {
> - * int data;
> - * struct foo *next;
> - * };
> + * Consider, for example, the following new task tracepoint:
> *
> - * struct bar {
> - * int data;
> - * struct foo f;
> - * };
> + * SEC("tp_btf/task_newtask")
> + * int BPF_PROG(new_task_tp, struct task_struct *task, u64 clone_flags)
> + * {
> + * ...
> + * }
> *
> - * struct foo *f = alloc_foo(); // Acquire kfunc
> - * struct bar *b = alloc_bar(); // Acquire kfunc
> + * And the following kfunc:
> *
> - * If a kfunc set_foo_data() wants to operate only on the allocated object, it
> - * will set the KF_TRUSTED_ARGS flag, which will prevent unsafe usage like:
> + * BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS)
> *
> - * set_foo_data(f, 42); // Allowed
> - * set_foo_data(f->next, 42); // Rejected, non-referenced pointer
> - * set_foo_data(&f->next, 42);// Rejected, referenced, but wrong type
> - * set_foo_data(&b->f, 42); // Rejected, referenced, but bad offset
> + * All invocations to the kfunc must pass the unmodified, unwalked task:
> *
> - * In the final case, usually for the purposes of type matching, it is deduced
> - * by looking at the type of the member at the offset, but due to the
> - * requirement of trusted argument, this deduction will be strict and not done
> - * for this case.
> + * bpf_task_acquire(task); // Allowed
> + * bpf_task_acquire(task->last_wakee); // Rejected, walked task
> + *
> + * Programs may also pass referenced tasks directly to the kfunc:
> + *
> + * struct task_struct *acquired;
> + *
> + * acquired = bpf_task_acquire(task); // Allowed, same as above
> + * bpf_task_acquire(acquired); // Allowed
> + * bpf_task_acquire(task); // Allowed
> + * bpf_task_acquire(acquired->last_wakee); // Rejected, walked task
> + *
> + * Programs may _not_, however, pass a task from an arbitrary fentry/fexit, or
> + * kprobe/kretprobe to the kfunc, as BPF cannot guarantee that all of these
> + * pointers are guaranteed to be safe. For example, the following BPF program
> + * would be rejected:
> + *
> + * SEC("kretprobe/free_task")
> + * int BPF_PROG(free_task_probe, struct task_struct *tsk)
> + * {
> + * struct task_struct *acquired;
> + *
> + * acquired = bpf_task_acquire(acquired); // Rejected, not a trusted pointer
> + * bpf_task_release(acquired);
> + *
> + * return 0;
> + * }
> */
> #define KF_TRUSTED_ARGS (1 << 4) /* kfunc only takes trusted pointer arguments */
> #define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 875355ff3718..8291f2911624 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -5579,6 +5579,11 @@ static u32 get_ctx_arg_idx(struct btf *btf, const struct btf_type *func_proto,
> return nr_args + 1;
> }
>
> +static bool prog_type_args_trusted(enum bpf_prog_type prog_type)
> +{
> + return prog_type == BPF_PROG_TYPE_TRACING || prog_type == BPF_PROG_TYPE_STRUCT_OPS;
> +}
> +
> bool btf_ctx_access(int off, int size, enum bpf_access_type type,
> const struct bpf_prog *prog,
> struct bpf_insn_access_aux *info)
> @@ -5722,6 +5727,9 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
> }
>
> info->reg_type = PTR_TO_BTF_ID;
> + if (prog_type_args_trusted(prog->type))
> + info->reg_type |= PTR_TRUSTED;
> +
> if (tgt_prog) {
> enum bpf_prog_type tgt_type;
>
> @@ -6558,15 +6566,26 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
> /* These register types have special constraints wrt ref_obj_id
> * and offset checks. The rest of trusted args don't.
> */
> - obj_ptr = reg->type == PTR_TO_CTX || reg->type == PTR_TO_BTF_ID ||
> + obj_ptr = reg->type == PTR_TO_CTX ||
> + base_type(reg->type) == PTR_TO_BTF_ID ||
> reg2btf_ids[base_type(reg->type)];
>
> /* Check if argument must be a referenced pointer, args + i has
> * been verified to be a pointer (after skipping modifiers).
> * PTR_TO_CTX is ok without having non-zero ref_obj_id.
> + *
> + * All object pointers must be refcounted, other than:
> + * - PTR_TO_CTX
> + * - PTR_TRUSTED pointers
> */
> - if (is_kfunc && trusted_args && (obj_ptr && reg->type != PTR_TO_CTX) && !reg->ref_obj_id) {
> - bpf_log(log, "R%d must be referenced\n", regno);
> + if (is_kfunc &&
> + trusted_args &&
> + obj_ptr &&
> + base_type(reg->type) != PTR_TO_CTX &&
> + (!(type_flag(reg->type) & PTR_TRUSTED) ||
> + (type_flag(reg->type) & ~PTR_TRUSTED)) &&
> + !reg->ref_obj_id) {
This is pretty hard to read.
Is this checking:
!(reg->type == PTR_TO_BTF_ID || reg->type == (PTR_TO_BTF_ID | PTR_TRUSTED))
?
Why not to use the above?
Similar in other places... type_flag(reg->type) & ~PTR_TRUSTED is not easy.
Maybe add a helper that will do
bool ff(reg)
{
return reg->type == PTR_TO_BTF_ID || reg->type == (PTR_TO_BTF_ID | PTR_TRUSTED);
}
?
> + bpf_log(log, "R%d must be referenced or trusted\n", regno);
> return -EINVAL;
> }
>
> @@ -6646,8 +6665,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
> i, btf_type_str(t));
> return -EINVAL;
> }
> - } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
> - (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
> + } else if (is_kfunc && (base_type(reg->type) == PTR_TO_BTF_ID ||
> + (reg2btf_ids[base_type(reg->type)]))) {
> const struct btf_type *reg_ref_t;
> const struct btf *reg_btf;
> const char *reg_ref_tname;
> @@ -6660,7 +6679,13 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
> return -EINVAL;
> }
>
> - if (reg->type == PTR_TO_BTF_ID) {
> + if ((type_flag(reg->type) & ~PTR_TRUSTED)) {
and use that helper here?
> + bpf_log(log, "kernel function %s arg#%d pointer had unexpected modifiers %d\n",
> + func_name, i, type_flag(reg->type));
> + return -EINVAL;
> + }
> +
> + if (base_type(reg->type) == PTR_TO_BTF_ID) {
> reg_btf = reg->btf;
> reg_ref_id = reg->btf_id;
> } else {
> @@ -6988,6 +7013,7 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
> }
>
> reg->type = PTR_TO_MEM | PTR_MAYBE_NULL;
> +
> reg->id = ++env->id_gen;
>
> continue;
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 0312d9ce292f..f5b6b1f969d9 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -543,7 +543,7 @@ static bool is_cmpxchg_insn(const struct bpf_insn *insn)
> static const char *reg_type_str(struct bpf_verifier_env *env,
> enum bpf_reg_type type)
> {
> - char postfix[16] = {0}, prefix[32] = {0};
> + char postfix[16] = {0}, prefix[64] = {0};
> static const char * const str[] = {
> [NOT_INIT] = "?",
> [SCALAR_VALUE] = "scalar",
> @@ -575,16 +575,14 @@ static const char *reg_type_str(struct bpf_verifier_env *env,
> strncpy(postfix, "_or_null", 16);
> }
>
> - if (type & MEM_RDONLY)
> - strncpy(prefix, "rdonly_", 32);
> - if (type & MEM_RINGBUF)
> - strncpy(prefix, "ringbuf_", 32);
> - if (type & MEM_USER)
> - strncpy(prefix, "user_", 32);
> - if (type & MEM_PERCPU)
> - strncpy(prefix, "percpu_", 32);
> - if (type & PTR_UNTRUSTED)
> - strncpy(prefix, "untrusted_", 32);
> + snprintf(prefix, sizeof(prefix), "%s%s%s%s%s%s",
> + type & MEM_RDONLY ? "rdonly_" : "",
> + type & MEM_RINGBUF ? "ringbuf_" : "",
> + type & MEM_USER ? "user_" : "",
> + type & MEM_PERCPU ? "percpu_" : "",
> + type & PTR_UNTRUSTED ? "untrusted_" : "",
> + type & PTR_TRUSTED ? "trusted_" : ""
> + );
>
> snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s%s",
> prefix, str[base_type(type)], postfix);
> @@ -3844,7 +3842,7 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
> struct bpf_reg_state *reg, u32 regno)
> {
> const char *targ_name = kernel_type_name(kptr_field->kptr.btf, kptr_field->kptr.btf_id);
> - int perm_flags = PTR_MAYBE_NULL;
> + int perm_flags = PTR_MAYBE_NULL | PTR_TRUSTED;
> const char *reg_name = "";
>
> /* Only unreferenced case accepts untrusted pointers */
> @@ -4707,6 +4705,9 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
> if (type_flag(reg->type) & PTR_UNTRUSTED)
> flag |= PTR_UNTRUSTED;
>
> + /* Any pointer obtained from walking a trusted pointer is no longer trusted. */
> + flag &= ~PTR_TRUSTED;
> +
> if (atype == BPF_READ && value_regno >= 0)
> mark_btf_ld_reg(env, regs, value_regno, ret, reg->btf, btf_id, flag);
>
> @@ -5774,6 +5775,7 @@ static const struct bpf_reg_types btf_id_sock_common_types = {
> PTR_TO_TCP_SOCK,
> PTR_TO_XDP_SOCK,
> PTR_TO_BTF_ID,
> + PTR_TO_BTF_ID | PTR_TRUSTED,
> },
> .btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
> };
> @@ -5807,9 +5809,19 @@ static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
> static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
> static const struct bpf_reg_types ringbuf_mem_types = { .types = { PTR_TO_MEM | MEM_RINGBUF } };
> static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
> -static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
> +static const struct bpf_reg_types btf_ptr_types = {
> + .types = {
> + PTR_TO_BTF_ID,
> + PTR_TO_BTF_ID | PTR_TRUSTED,
> + },
> +};
> static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
> -static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_BTF_ID | MEM_PERCPU } };
> +static const struct bpf_reg_types percpu_btf_ptr_types = {
> + .types = {
> + PTR_TO_BTF_ID | MEM_PERCPU,
> + PTR_TO_BTF_ID | MEM_PERCPU | PTR_TRUSTED,
> + }
> +};
> static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } };
> static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } };
> static const struct bpf_reg_types const_str_ptr_types = { .types = { PTR_TO_MAP_VALUE } };
> @@ -5897,7 +5909,7 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
> return -EACCES;
>
> found:
> - if (reg->type == PTR_TO_BTF_ID) {
> + if (base_type(reg->type) == PTR_TO_BTF_ID && !(type_flag(reg->type) & ~PTR_TRUSTED)) {
> /* For bpf_sk_release, it needs to match against first member
> * 'struct sock_common', hence make an exception for it. This
> * allows bpf_sk_release to work for multiple socket types.
> @@ -5973,6 +5985,7 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
> * fixed offset.
> */
> case PTR_TO_BTF_ID:
> + case PTR_TO_BTF_ID | PTR_TRUSTED:
> /* When referenced PTR_TO_BTF_ID is passed to release function,
> * it's fixed offset must be 0. In the other cases, fixed offset
> * can be non-zero.
> @@ -13690,6 +13703,8 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
> break;
> case PTR_TO_BTF_ID:
> case PTR_TO_BTF_ID | PTR_UNTRUSTED:
> + case PTR_TO_BTF_ID | PTR_TRUSTED:
> + case PTR_TO_BTF_ID | PTR_UNTRUSTED | PTR_TRUSTED:
> if (type == BPF_READ) {
> insn->code = BPF_LDX | BPF_PROBE_MEM |
> BPF_SIZE((insn)->code);
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index f2d8d070d024..5b9008bc597b 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -774,7 +774,7 @@ BPF_CALL_0(bpf_get_current_task_btf)
> const struct bpf_func_proto bpf_get_current_task_btf_proto = {
> .func = bpf_get_current_task_btf,
> .gpl_only = true,
> - .ret_type = RET_PTR_TO_BTF_ID,
> + .ret_type = RET_PTR_TO_BTF_ID_TRUSTED,
> .ret_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK],
> };
>
> diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
> index d15c91de995f..0006b5438ff7 100644
> --- a/net/ipv4/bpf_tcp_ca.c
> +++ b/net/ipv4/bpf_tcp_ca.c
> @@ -61,7 +61,9 @@ static bool bpf_tcp_ca_is_valid_access(int off, int size,
> if (!bpf_tracing_btf_ctx_access(off, size, type, prog, info))
> return false;
>
> - if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
> + if (base_type(info->reg_type) == PTR_TO_BTF_ID &&
> + !(type_flag(info->reg_type) & ~PTR_TRUSTED) &&
> + info->btf_id == sock_id)
> /* promote it to tcp_sock */
> info->btf_id = tcp_sock_id;
>
> diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
> index e1a937277b54..7ac947f00df4 100644
> --- a/tools/testing/selftests/bpf/verifier/calls.c
> +++ b/tools/testing/selftests/bpf/verifier/calls.c
> @@ -109,7 +109,7 @@
> },
> .prog_type = BPF_PROG_TYPE_SCHED_CLS,
> .result = REJECT,
> - .errstr = "arg#0 pointer type STRUCT prog_test_ref_kfunc must point",
> + .errstr = "arg#0 pointer had unexpected modifiers",
> .fixup_kfunc_btf_id = {
> { "bpf_kfunc_call_test_acquire", 3 },
> { "bpf_kfunc_call_test_release", 5 },
> diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
> index fd683a32a276..d9367f2894b9 100644
> --- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
> +++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
> @@ -142,7 +142,7 @@
> .kfunc = "bpf",
> .expected_attach_type = BPF_LSM_MAC,
> .flags = BPF_F_SLEEPABLE,
> - .errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
> + .errstr = "arg#0 pointer had unexpected modifiers",
> .fixup_kfunc_btf_id = {
> { "bpf_lookup_user_key", 2 },
> { "bpf_key_put", 4 },
> @@ -163,7 +163,7 @@
> .kfunc = "bpf",
> .expected_attach_type = BPF_LSM_MAC,
> .flags = BPF_F_SLEEPABLE,
> - .errstr = "arg#0 pointer type STRUCT bpf_key must point to scalar, or struct with scalar",
> + .errstr = "arg#0 pointer had unexpected modifiers",
> .fixup_kfunc_btf_id = {
> { "bpf_lookup_system_key", 1 },
> { "bpf_key_put", 3 },
> --
> 2.38.1
>