For struct_ops progs, whether a particular prog uses private stack
depends on prog->aux->priv_stack_requested setting before actual
insn-level verification for that prog. One particular implementation
is to piggyback on struct_ops->check_member(). The next patch has
an example for this. The struct_ops->check_member() sets
prog->aux->priv_stack_requested to be true which enables private stack
usage.
The struct_ops prog follows the same rule as kprobe/tracing progs after
function bpf_enable_priv_stack(). For example, even a struct_ops prog
requests private stack, it could still use normal kernel stack if
the stack size is small (< 64 bytes).
The prog->aux->priv_stack_requested is also used for recursion checking
for struct_ops progs. Similar to tracing progs, nested same cpu same
prog run will be skipped. A field (recursion_detected()) is added to
bpf_prog_aux structure. If bpf_prog->aux->recursion_detected
is implemented by the struct_ops subsystem and nested same cpu/prog
happens, the function will be triggered to report an error, collect
related info, etc.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
include/linux/bpf.h | 1 +
include/linux/bpf_verifier.h | 1 +
kernel/bpf/trampoline.c | 4 ++++
kernel/bpf/verifier.c | 6 ++++++
4 files changed, 12 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 644ad35b88ec..938e9c4fa9b1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1528,6 +1528,7 @@ struct bpf_prog_aux {
u64 prog_array_member_cnt; /* counts how many times as member of prog_array */
struct mutex ext_mutex; /* mutex for is_extended and prog_array_member_cnt */
struct bpf_arena *arena;
+ void (*recursion_detected)(struct bpf_prog *prog); /* callback if recursion is detected */
/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
const struct btf_type *attach_func_proto;
/* function name for valid attach_btf_id */
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 456fd2265345..6c1a173c30e6 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -895,6 +895,7 @@ static inline bool bpf_prog_check_recur(const struct bpf_prog *prog)
case BPF_PROG_TYPE_TRACING:
return prog->expected_attach_type != BPF_TRACE_ITER;
case BPF_PROG_TYPE_STRUCT_OPS:
+ return prog->aux->priv_stack_requested;
case BPF_PROG_TYPE_LSM:
return false;
default:
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 9f36c049f4c2..a8d188b31da5 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -899,6 +899,8 @@ static u64 notrace __bpf_prog_enter_recur(struct bpf_prog *prog, struct bpf_tram
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
bpf_prog_inc_misses_counter(prog);
+ if (prog->aux->recursion_detected)
+ prog->aux->recursion_detected(prog);
return 0;
}
return bpf_prog_start_time();
@@ -975,6 +977,8 @@ u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog,
if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
bpf_prog_inc_misses_counter(prog);
+ if (prog->aux->recursion_detected)
+ prog->aux->recursion_detected(prog);
return 0;
}
return bpf_prog_start_time();
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 09bb9dc939d6..d0e5038a844a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6279,6 +6279,7 @@ static int check_max_stack_depth(struct bpf_verifier_env *env)
}
}
+ env->prog->aux->priv_stack_requested = false;
if (si[0].priv_stack_mode == PRIV_STACK_ADAPTIVE)
env->prog->aux->priv_stack_requested = true;
@@ -21986,6 +21987,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
}
}
+ if (prog->aux->priv_stack_requested && !bpf_jit_supports_private_stack()) {
+ verbose(env, "Private stack not supported by jit\n");
+ return -EACCES;
+ }
+
/* btf_ctx_access() used this to provide argument type info */
prog->aux->ctx_arg_info =
st_ops_desc->arg_info[member_idx].info;
--
2.43.5
