On 2/21/21 9:09 PM, Björn Töpel wrote:
From: Björn Töpel <bjorn.topel@xxxxxxxxx>
Currently the bpf_redirect_map() implementation dispatches to the
correct map-lookup function via a switch-statement. To avoid the
dispatching, this change adds one bpf_redirect_map() implementation per
map. Correct function is automatically selected by the BPF verifier.
v2->v3 : Fix build when CONFIG_NET is not set. (lkp)
v1->v2 : Re-added comment. (Toke)
rfc->v1: Get rid of the macro and use __always_inline. (Jesper)
Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx>
[...]
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3d34ba492d46..89ccc10c6348 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5409,7 +5409,8 @@ record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
func_id != BPF_FUNC_map_delete_elem &&
func_id != BPF_FUNC_map_push_elem &&
func_id != BPF_FUNC_map_pop_elem &&
- func_id != BPF_FUNC_map_peek_elem)
+ func_id != BPF_FUNC_map_peek_elem &&
+ func_id != BPF_FUNC_redirect_map)
return 0;
if (map == NULL) {
@@ -11545,12 +11546,12 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
struct bpf_prog *prog = env->prog;
bool expect_blinding = bpf_jit_blinding_enabled(prog);
struct bpf_insn *insn = prog->insnsi;
- const struct bpf_func_proto *fn;
const int insn_cnt = prog->len;
const struct bpf_map_ops *ops;
struct bpf_insn_aux_data *aux;
struct bpf_insn insn_buf[16];
struct bpf_prog *new_prog;
+ bpf_func_proto_func func;
struct bpf_map *map_ptr;
int i, ret, cnt, delta = 0;
@@ -11860,17 +11861,23 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
}
patch_call_imm:
- fn = env->ops->get_func_proto(insn->imm, env->prog);
+ if (insn->imm == BPF_FUNC_redirect_map) {
+ aux = &env->insn_aux_data[i];
+ map_ptr = BPF_MAP_PTR(aux->map_ptr_state);
+ func = get_xdp_redirect_func(map_ptr->map_type);
Nope, this is broken. :/ The map_ptr could be poisoned, so unconditionally fetching
map_ptr->map_type can crash the box for specially crafted BPF progs.
Also, given you add the related BPF_CALL_3() functions below, what is the reason
to not properly integrate this like the map ops near patch_map_ops_generic?
+ } else {
+ func = env->ops->get_func_proto(insn->imm, env->prog)->func;
+ }
/* all functions that have prototype and verifier allowed
* programs to call them, must be real in-kernel functions
*/
- if (!fn->func) {
+ if (!func) {
verbose(env,
"kernel subsystem misconfigured func %s#%d\n",
func_id_name(insn->imm), insn->imm);
return -EFAULT;
}
- insn->imm = fn->func - __bpf_call_base;
+ insn->imm = func - __bpf_call_base;
}
/* Since poke tab is now finalized, publish aux to tracker. */
diff --git a/net/core/filter.c b/net/core/filter.c
index adfdad234674..502e7856f107 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3944,22 +3944,6 @@ void xdp_do_flush(void)
}
EXPORT_SYMBOL_GPL(xdp_do_flush);
-static inline void *__xdp_map_lookup_elem(struct bpf_map *map, u32 index)
-{
- switch (map->map_type) {
- case BPF_MAP_TYPE_DEVMAP:
- return __dev_map_lookup_elem(map, index);
- case BPF_MAP_TYPE_DEVMAP_HASH:
- return __dev_map_hash_lookup_elem(map, index);
- case BPF_MAP_TYPE_CPUMAP:
- return __cpu_map_lookup_elem(map, index);
- case BPF_MAP_TYPE_XSKMAP:
- return __xsk_map_lookup_elem(map, index);
- default:
- return NULL;
- }
-}
-
void bpf_clear_redirect_map(struct bpf_map *map)
{
struct bpf_redirect_info *ri;
@@ -4110,8 +4094,9 @@ static const struct bpf_func_proto bpf_xdp_redirect_proto = {
.arg2_type = ARG_ANYTHING,
};
-BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex,
- u64, flags)
+static __always_inline s64 __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifindex, u64 flags,
+ void *lookup_elem(struct bpf_map *map,
+ u32 key))
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
@@ -4119,7 +4104,7 @@ BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex,
if (unlikely(flags > XDP_TX))
return XDP_ABORTED;
- ri->tgt_value = __xdp_map_lookup_elem(map, ifindex);
+ ri->tgt_value = lookup_elem(map, ifindex);
if (unlikely(!ri->tgt_value)) {
/* If the lookup fails we want to clear out the state in the
* redirect_info struct completely, so that if an eBPF program
@@ -4137,8 +4122,44 @@ BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex,
return XDP_REDIRECT;
}
+BPF_CALL_3(bpf_xdp_redirect_devmap, struct bpf_map *, map, u32, ifindex, u64, flags)
+{
+ return __bpf_xdp_redirect_map(map, ifindex, flags, __dev_map_lookup_elem);
+}
+
+BPF_CALL_3(bpf_xdp_redirect_devmap_hash, struct bpf_map *, map, u32, ifindex, u64, flags)
+{
+ return __bpf_xdp_redirect_map(map, ifindex, flags, __dev_map_hash_lookup_elem);
+}
+
+BPF_CALL_3(bpf_xdp_redirect_cpumap, struct bpf_map *, map, u32, ifindex, u64, flags)
+{
+ return __bpf_xdp_redirect_map(map, ifindex, flags, __cpu_map_lookup_elem);
+}
+
+BPF_CALL_3(bpf_xdp_redirect_xskmap, struct bpf_map *, map, u32, ifindex, u64, flags)
+{
+ return __bpf_xdp_redirect_map(map, ifindex, flags, __xsk_map_lookup_elem);
+}
+
+bpf_func_proto_func get_xdp_redirect_func(enum bpf_map_type map_type)
+{
+ switch (map_type) {
+ case BPF_MAP_TYPE_DEVMAP:
+ return bpf_xdp_redirect_devmap;
+ case BPF_MAP_TYPE_DEVMAP_HASH:
+ return bpf_xdp_redirect_devmap_hash;
+ case BPF_MAP_TYPE_CPUMAP:
+ return bpf_xdp_redirect_cpumap;
+ case BPF_MAP_TYPE_XSKMAP:
+ return bpf_xdp_redirect_xskmap;
+ default:
+ return NULL;
+ }
+}
+
+/* NB! .func is NULL! get_xdp_redirect_func() is used instead! */
static const struct bpf_func_proto bpf_xdp_redirect_map_proto = {
- .func = bpf_xdp_redirect_map,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_CONST_MAP_PTR,
