bpf: fix check_map_func_compatibility logic

The commit 35578d798400 ("bpf: Implement function bpf_perf_event_read() that get the selected hardware PMU conuter")
introduced clever way to check bpf_helper<->map_type compatibility.
Later on commit a43eec304259 ("bpf: introduce bpf_perf_event_output() helper") adjusted
the logic and inadvertently broke it.
Get rid of the clever bool compare and go back to two-way check
from map and from helper perspective.

Fixes: a43eec304259 ("bpf: introduce bpf_perf_event_output() helper")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 89bcaa0966da06b3510d1d3554aace105f77f19d..c5c17a62f509f67385cfb9a587e702646cc19b80 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -239,16 +239,6 @@ static const char * const reg_type_str[] = {
        [CONST_IMM]             = "imm",
 };
 
-static const struct {
-       int map_type;
-       int func_id;
-} func_limit[] = {
-       {BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
-       {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
-       {BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
-       {BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid},
-};
-
 static void print_verifier_state(struct verifier_env *env)
 {
        enum bpf_reg_type t;
@@ -921,27 +911,52 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 
 static int check_map_func_compatibility(struct bpf_map *map, int func_id)
 {
-       bool bool_map, bool_func;
-       int i;
-
        if (!map)
                return 0;
 
-       for (i = 0; i < ARRAY_SIZE(func_limit); i++) {
-               bool_map = (map->map_type == func_limit[i].map_type);
-               bool_func = (func_id == func_limit[i].func_id);
-               /* only when map & func pair match it can continue.
-                * don't allow any other map type to be passed into
-                * the special func;
-                */
-               if (bool_func && bool_map != bool_func) {
-                       verbose("cannot pass map_type %d into func %d\n",
-                               map->map_type, func_id);
-                       return -EINVAL;
-               }
+       /* We need a two way check, first is from map perspective ... */
+       switch (map->map_type) {
+       case BPF_MAP_TYPE_PROG_ARRAY:
+               if (func_id != BPF_FUNC_tail_call)
+                       goto error;
+               break;
+       case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
+               if (func_id != BPF_FUNC_perf_event_read &&
+                   func_id != BPF_FUNC_perf_event_output)
+                       goto error;
+               break;
+       case BPF_MAP_TYPE_STACK_TRACE:
+               if (func_id != BPF_FUNC_get_stackid)
+                       goto error;
+               break;
+       default:
+               break;
+       }
+
+       /* ... and second from the function itself. */
+       switch (func_id) {
+       case BPF_FUNC_tail_call:
+               if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
+                       goto error;
+               break;
+       case BPF_FUNC_perf_event_read:
+       case BPF_FUNC_perf_event_output:
+               if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
+                       goto error;
+               break;
+       case BPF_FUNC_get_stackid:
+               if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
+                       goto error;
+               break;
+       default:
+               break;
        }
 
        return 0;
+error:
+       verbose("cannot pass map_type %d into func %d\n",
+               map->map_type, func_id);
+       return -EINVAL;
 }
 
 static int check_call(struct verifier_env *env, int func_id)