Merge branch 'Add support for kptrs in more BPF maps'

Kumar Kartikeya Dwivedi says:

====================

This set adds support for kptrs in percpu hashmaps, percpu LRU hashmaps,
and local storage maps (covering sk, cgrp, task, inode).

Tests are expanded to test more existing maps at runtime and also test
the code path for the local storage maps (which is shared by all
implementations).

A question for reviewers is what the position of the BPF runtime should
be on dealing with reference cycles that can be created by BPF programs
at runtime using this additional support. For instance, one can store
the kptr of the task in its own task local storage, creating a cycle
which prevents destruction of task local storage. Cycles can be formed
using arbitrarily long kptr ownership chains. Therefore, just preventing
storage of such kptrs in some maps is not a sufficient solution, and is
more likely to hurt usability.

There is precedence in existing runtimes which promise memory safety,
like Rust, where reference cycles and memory leaks are permitted.
However, traditionally the safety guarantees of BPF have been stronger.
Thus, more discussion and thought is invited on this topic to ensure we
cover all usage aspects.

Changelog:
----------
v2 -> v3
v2: https://lore.kernel.org/bpf/20230221200646.2500777-1-memxor@gmail.com/

 * Fix a use-after-free bug in local storage patch
 * Fix selftest for aarch64 (don't use fentry/fmod_ret)
 * Wait for RCU Tasks Trace GP along with RCU GP in selftest

v1 -> v2
v1: https://lore.kernel.org/bpf/20230219155249.1755998-1-memxor@gmail.com

 * Simplify selftests, fix a couple of bugs
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/linux/bpf_local_storage.h

@@ -74,6 +74,12 @@ struct bpf_local_storage_elem {
 	struct hlist_node snode;	/* Linked to bpf_local_storage */
 	struct bpf_local_storage __rcu *local_storage;
 	struct rcu_head rcu;
+	bool can_use_smap; /* Is it safe to access smap in bpf_selem_free_* RCU
+			    * callbacks? bpf_local_storage_map_free only
+			    * executes rcu_barrier when there are special
+			    * fields, this field remembers that to ensure we
+			    * don't access already freed smap in sdata.
+			    */
 	/* 8 bytes hole */
 	/* The data is stored in another cacheline to minimize
 	 * the number of cachelines access during a cache hit.

kernel/bpf/bpf_local_storage.c

@@ -85,6 +85,7 @@ bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
 	if (selem) {
 		if (value)
 			copy_map_value(&smap->map, SDATA(selem)->data, value);
+		/* No need to call check_and_init_map_value as memory is zero init */
 		return selem;
 	}
 
@@ -113,10 +114,25 @@ static void bpf_selem_free_rcu(struct rcu_head *rcu)
 	struct bpf_local_storage_elem *selem;
 
 	selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
-	if (rcu_trace_implies_rcu_gp())
+	/* The can_use_smap bool is set whenever we need to free additional
+	 * fields in selem data before freeing selem. bpf_local_storage_map_free
+	 * only executes rcu_barrier to wait for RCU callbacks when it has
+	 * special fields, hence we can only conditionally dereference smap, as
+	 * by this time the map might have already been freed without waiting
+	 * for our call_rcu callback if it did not have any special fields.
+	 */
+	if (selem->can_use_smap)
+		bpf_obj_free_fields(SDATA(selem)->smap->map.record, SDATA(selem)->data);
 	kfree(selem);
+}
+
+static void bpf_selem_free_tasks_trace_rcu(struct rcu_head *rcu)
+{
+	/* Free directly if Tasks Trace RCU GP also implies RCU GP */
+	if (rcu_trace_implies_rcu_gp())
+		bpf_selem_free_rcu(rcu);
 	else
-		kfree_rcu(selem, rcu);
+		call_rcu(rcu, bpf_selem_free_rcu);
 }
 
 /* local_storage->lock must be held and selem->local_storage == local_storage.
@@ -170,9 +186,9 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
 		RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
 
 	if (use_trace_rcu)
-		call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_rcu);
+		call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_tasks_trace_rcu);
 	else
-		kfree_rcu(selem, rcu);
+		call_rcu(&selem->rcu, bpf_selem_free_rcu);
 
 	return free_local_storage;
 }
@@ -240,6 +256,11 @@ void bpf_selem_link_map(struct bpf_local_storage_map *smap,
 	RCU_INIT_POINTER(SDATA(selem)->smap, smap);
 	hlist_add_head_rcu(&selem->map_node, &b->list);
 	raw_spin_unlock_irqrestore(&b->lock, flags);
+
+	/* If our data will have special fields, smap will wait for us to use
+	 * its record in bpf_selem_free_* RCU callbacks before freeing itself.
+	 */
+	selem->can_use_smap = !IS_ERR_OR_NULL(smap->map.record);
 }
 
 void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu)
@@ -723,6 +744,25 @@ void bpf_local_storage_map_free(struct bpf_map *map,
 	 */
 	synchronize_rcu();
 
+	/* Only delay freeing of smap, buckets are not needed anymore */
 	kvfree(smap->buckets);
+
+	/* When local storage has special fields, callbacks for
+	 * bpf_selem_free_rcu and bpf_selem_free_tasks_trace_rcu will keep using
+	 * the map BTF record, we need to execute an RCU barrier to wait for
+	 * them as the record will be freed right after our map_free callback.
+	 */
+	if (!IS_ERR_OR_NULL(smap->map.record)) {
+		rcu_barrier_tasks_trace();
+		/* We cannot skip rcu_barrier() when rcu_trace_implies_rcu_gp()
+		 * is true, because while call_rcu invocation is skipped in that
+		 * case in bpf_selem_free_tasks_trace_rcu (and all local storage
+		 * maps pass use_trace_rcu = true), there can be call_rcu
+		 * callbacks based on use_trace_rcu = false in the earlier while
+		 * ((selem = ...)) loop or from bpf_local_storage_unlink_nolock
+		 * called from owner's free path.
+		 */
+		rcu_barrier();
+	}
 	bpf_map_area_free(smap);
 }

kernel/bpf/hashtab.c

@@ -249,9 +249,20 @@ static void htab_free_prealloced_fields(struct bpf_htab *htab)
 		struct htab_elem *elem;
 
 		elem = get_htab_elem(htab, i);
+		if (htab_is_percpu(htab)) {
+			void __percpu *pptr = htab_elem_get_ptr(elem, htab->map.key_size);
+			int cpu;
+
+			for_each_possible_cpu(cpu) {
+				bpf_obj_free_fields(htab->map.record, per_cpu_ptr(pptr, cpu));
+				cond_resched();
+			}
+		} else {
 			bpf_obj_free_fields(htab->map.record, elem->key + round_up(htab->map.key_size, 8));
 			cond_resched();
 		}
+		cond_resched();
+	}
 }
 
 static void htab_free_elems(struct bpf_htab *htab)
@@ -759,9 +770,17 @@ static int htab_lru_map_gen_lookup(struct bpf_map *map,
 static void check_and_free_fields(struct bpf_htab *htab,
 				  struct htab_elem *elem)
 {
+	if (htab_is_percpu(htab)) {
+		void __percpu *pptr = htab_elem_get_ptr(elem, htab->map.key_size);
+		int cpu;
+
+		for_each_possible_cpu(cpu)
+			bpf_obj_free_fields(htab->map.record, per_cpu_ptr(pptr, cpu));
+	} else {
 		void *map_value = elem->key + round_up(htab->map.key_size, 8);
 
 		bpf_obj_free_fields(htab->map.record, map_value);
+	}
 }
 
 /* It is called from the bpf_lru_list when the LRU needs to delete
@@ -858,9 +877,9 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 
 static void htab_elem_free(struct bpf_htab *htab, struct htab_elem *l)
 {
+	check_and_free_fields(htab, l);
 	if (htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH)
 		bpf_mem_cache_free(&htab->pcpu_ma, l->ptr_to_pptr);
-	check_and_free_fields(htab, l);
 	bpf_mem_cache_free(&htab->ma, l);
 }
 
@@ -918,14 +937,13 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
 {
 	if (!onallcpus) {
 		/* copy true value_size bytes */
-		memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
+		copy_map_value(&htab->map, this_cpu_ptr(pptr), value);
 	} else {
 		u32 size = round_up(htab->map.value_size, 8);
 		int off = 0, cpu;
 
 		for_each_possible_cpu(cpu) {
-			bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
-					value + off, size);
+			copy_map_value_long(&htab->map, per_cpu_ptr(pptr, cpu), value + off);
 			off += size;
 		}
 	}
@@ -940,16 +958,14 @@ static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
 	 * (onallcpus=false always when coming from bpf prog).
 	 */
 	if (!onallcpus) {
-		u32 size = round_up(htab->map.value_size, 8);
 		int current_cpu = raw_smp_processor_id();
 		int cpu;
 
 		for_each_possible_cpu(cpu) {
 			if (cpu == current_cpu)
-				bpf_long_memcpy(per_cpu_ptr(pptr, cpu), value,
-						size);
-			else
-				memset(per_cpu_ptr(pptr, cpu), 0, size);
+				copy_map_value_long(&htab->map, per_cpu_ptr(pptr, cpu), value);
+			else /* Since elem is preallocated, we cannot touch special fields */
+				zero_map_value(&htab->map, per_cpu_ptr(pptr, cpu));
 		}
 	} else {
 		pcpu_copy_value(htab, pptr, value, onallcpus);
@@ -1575,9 +1591,8 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
 
 			pptr = htab_elem_get_ptr(l, key_size);
 			for_each_possible_cpu(cpu) {
-				bpf_long_memcpy(value + off,
-						per_cpu_ptr(pptr, cpu),
-						roundup_value_size);
+				copy_map_value_long(&htab->map, value + off, per_cpu_ptr(pptr, cpu));
+				check_and_init_map_value(&htab->map, value + off);
 				off += roundup_value_size;
 			}
 		} else {
@@ -1772,8 +1787,8 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 
 			pptr = htab_elem_get_ptr(l, map->key_size);
 			for_each_possible_cpu(cpu) {
-				bpf_long_memcpy(dst_val + off,
-						per_cpu_ptr(pptr, cpu), size);
+				copy_map_value_long(&htab->map, dst_val + off, per_cpu_ptr(pptr, cpu));
+				check_and_init_map_value(&htab->map, dst_val + off);
 				off += size;
 			}
 		} else {
@@ -2046,9 +2061,9 @@ static int __bpf_hash_map_seq_show(struct seq_file *seq, struct htab_elem *elem)
 				roundup_value_size = round_up(map->value_size, 8);
 				pptr = htab_elem_get_ptr(elem, map->key_size);
 				for_each_possible_cpu(cpu) {
-					bpf_long_memcpy(info->percpu_value_buf + off,
-							per_cpu_ptr(pptr, cpu),
-							roundup_value_size);
+					copy_map_value_long(map, info->percpu_value_buf + off,
+							    per_cpu_ptr(pptr, cpu));
+					check_and_init_map_value(map, info->percpu_value_buf + off);
 					off += roundup_value_size;
 				}
 				ctx.value = info->percpu_value_buf;
@@ -2292,8 +2307,8 @@ int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
 	 */
 	pptr = htab_elem_get_ptr(l, map->key_size);
 	for_each_possible_cpu(cpu) {
-		bpf_long_memcpy(value + off,
-				per_cpu_ptr(pptr, cpu), size);
+		copy_map_value_long(map, value + off, per_cpu_ptr(pptr, cpu));
+		check_and_init_map_value(map, value + off);
 		off += size;
 	}
 	ret = 0;

kernel/bpf/syscall.c

@@ -1059,9 +1059,15 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
 			case BPF_KPTR_UNREF:
 			case BPF_KPTR_REF:
 				if (map->map_type != BPF_MAP_TYPE_HASH &&
+				    map->map_type != BPF_MAP_TYPE_PERCPU_HASH &&
 				    map->map_type != BPF_MAP_TYPE_LRU_HASH &&
+				    map->map_type != BPF_MAP_TYPE_LRU_PERCPU_HASH &&
 				    map->map_type != BPF_MAP_TYPE_ARRAY &&
-				    map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY) {
+				    map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY &&
+				    map->map_type != BPF_MAP_TYPE_SK_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_INODE_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_TASK_STORAGE &&
+				    map->map_type != BPF_MAP_TYPE_CGRP_STORAGE) {
 					ret = -EOPNOTSUPP;
 					goto free_map_tab;
 				}

kernel/bpf/verifier.c

@@ -7222,22 +7222,26 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
 		break;
 	case BPF_MAP_TYPE_SK_STORAGE:
 		if (func_id != BPF_FUNC_sk_storage_get &&
-		    func_id != BPF_FUNC_sk_storage_delete)
+		    func_id != BPF_FUNC_sk_storage_delete &&
+		    func_id != BPF_FUNC_kptr_xchg)
 			goto error;
 		break;
 	case BPF_MAP_TYPE_INODE_STORAGE:
 		if (func_id != BPF_FUNC_inode_storage_get &&
-		    func_id != BPF_FUNC_inode_storage_delete)
+		    func_id != BPF_FUNC_inode_storage_delete &&
+		    func_id != BPF_FUNC_kptr_xchg)
 			goto error;
 		break;
 	case BPF_MAP_TYPE_TASK_STORAGE:
 		if (func_id != BPF_FUNC_task_storage_get &&
-		    func_id != BPF_FUNC_task_storage_delete)
+		    func_id != BPF_FUNC_task_storage_delete &&
+		    func_id != BPF_FUNC_kptr_xchg)
 			goto error;
 		break;
 	case BPF_MAP_TYPE_CGRP_STORAGE:
 		if (func_id != BPF_FUNC_cgrp_storage_get &&
-		    func_id != BPF_FUNC_cgrp_storage_delete)
+		    func_id != BPF_FUNC_cgrp_storage_delete &&
+		    func_id != BPF_FUNC_kptr_xchg)
 			goto error;
 		break;
 	case BPF_MAP_TYPE_BLOOM_FILTER:

tools/testing/selftests/bpf/prog_tests/map_kptr.c

@@ -4,70 +4,160 @@
 
 #include "map_kptr.skel.h"
 #include "map_kptr_fail.skel.h"
+#include "rcu_tasks_trace_gp.skel.h"
 
 static void test_map_kptr_success(bool test_run)
 {
+	LIBBPF_OPTS(bpf_test_run_opts, lopts);
 	LIBBPF_OPTS(bpf_test_run_opts, opts,
 		.data_in = &pkt_v4,
 		.data_size_in = sizeof(pkt_v4),
 		.repeat = 1,
 	);
+	int key = 0, ret, cpu;
 	struct map_kptr *skel;
-	int key = 0, ret;
-	char buf[16];
+	char buf[16], *pbuf;
 
 	skel = map_kptr__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "map_kptr__open_and_load"))
 		return;
 
-	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref), &opts);
-	ASSERT_OK(ret, "test_map_kptr_ref refcount");
-	ASSERT_OK(opts.retval, "test_map_kptr_ref retval");
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref1), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref1 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref1 retval");
 	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref2), &opts);
 	ASSERT_OK(ret, "test_map_kptr_ref2 refcount");
 	ASSERT_OK(opts.retval, "test_map_kptr_ref2 retval");
 
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_ls_map_kptr_ref1), &lopts);
+	ASSERT_OK(ret, "test_ls_map_kptr_ref1 refcount");
+	ASSERT_OK(lopts.retval, "test_ls_map_kptr_ref1 retval");
+
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_ls_map_kptr_ref2), &lopts);
+	ASSERT_OK(ret, "test_ls_map_kptr_ref2 refcount");
+	ASSERT_OK(lopts.retval, "test_ls_map_kptr_ref2 retval");
+
 	if (test_run)
 		goto exit;
 
+	cpu = libbpf_num_possible_cpus();
+	if (!ASSERT_GT(cpu, 0, "libbpf_num_possible_cpus"))
+		goto exit;
+
+	pbuf = calloc(cpu, sizeof(buf));
+	if (!ASSERT_OK_PTR(pbuf, "calloc(pbuf)"))
+		goto exit;
+
 	ret = bpf_map__update_elem(skel->maps.array_map,
 				   &key, sizeof(key), buf, sizeof(buf), 0);
 	ASSERT_OK(ret, "array_map update");
-	ret = bpf_map__update_elem(skel->maps.array_map,
-				   &key, sizeof(key), buf, sizeof(buf), 0);
-	ASSERT_OK(ret, "array_map update2");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
+
+	ret = bpf_map__update_elem(skel->maps.pcpu_array_map,
+				   &key, sizeof(key), pbuf, cpu * sizeof(buf), 0);
+	ASSERT_OK(ret, "pcpu_array_map update");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
 
-	ret = bpf_map__update_elem(skel->maps.hash_map,
-				   &key, sizeof(key), buf, sizeof(buf), 0);
-	ASSERT_OK(ret, "hash_map update");
 	ret = bpf_map__delete_elem(skel->maps.hash_map, &key, sizeof(key), 0);
 	ASSERT_OK(ret, "hash_map delete");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
+
+	ret = bpf_map__delete_elem(skel->maps.pcpu_hash_map, &key, sizeof(key), 0);
+	ASSERT_OK(ret, "pcpu_hash_map delete");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
 
-	ret = bpf_map__update_elem(skel->maps.hash_malloc_map,
-				   &key, sizeof(key), buf, sizeof(buf), 0);
-	ASSERT_OK(ret, "hash_malloc_map update");
 	ret = bpf_map__delete_elem(skel->maps.hash_malloc_map, &key, sizeof(key), 0);
 	ASSERT_OK(ret, "hash_malloc_map delete");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
+
+	ret = bpf_map__delete_elem(skel->maps.pcpu_hash_malloc_map, &key, sizeof(key), 0);
+	ASSERT_OK(ret, "pcpu_hash_malloc_map delete");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
 
-	ret = bpf_map__update_elem(skel->maps.lru_hash_map,
-				   &key, sizeof(key), buf, sizeof(buf), 0);
-	ASSERT_OK(ret, "lru_hash_map update");
 	ret = bpf_map__delete_elem(skel->maps.lru_hash_map, &key, sizeof(key), 0);
 	ASSERT_OK(ret, "lru_hash_map delete");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
+
+	ret = bpf_map__delete_elem(skel->maps.lru_pcpu_hash_map, &key, sizeof(key), 0);
+	ASSERT_OK(ret, "lru_pcpu_hash_map delete");
+	skel->data->ref--;
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_map_kptr_ref3), &opts);
+	ASSERT_OK(ret, "test_map_kptr_ref3 refcount");
+	ASSERT_OK(opts.retval, "test_map_kptr_ref3 retval");
 
+	ret = bpf_prog_test_run_opts(bpf_program__fd(skel->progs.test_ls_map_kptr_ref_del), &lopts);
+	ASSERT_OK(ret, "test_ls_map_kptr_ref_del delete");
+	skel->data->ref--;
+	ASSERT_OK(lopts.retval, "test_ls_map_kptr_ref_del retval");
+
+	free(pbuf);
 exit:
 	map_kptr__destroy(skel);
 }
 
-void test_map_kptr(void)
+static int kern_sync_rcu_tasks_trace(struct rcu_tasks_trace_gp *rcu)
+{
+	long gp_seq = READ_ONCE(rcu->bss->gp_seq);
+	LIBBPF_OPTS(bpf_test_run_opts, opts);
+
+	if (!ASSERT_OK(bpf_prog_test_run_opts(bpf_program__fd(rcu->progs.do_call_rcu_tasks_trace),
+					      &opts), "do_call_rcu_tasks_trace"))
+		return -EFAULT;
+	if (!ASSERT_OK(opts.retval, "opts.retval == 0"))
+		return -EFAULT;
+	while (gp_seq == READ_ONCE(rcu->bss->gp_seq))
+		sched_yield();
+	return 0;
+}
+
+void serial_test_map_kptr(void)
 {
-	if (test__start_subtest("success")) {
+	struct rcu_tasks_trace_gp *skel;
+
+	RUN_TESTS(map_kptr_fail);
+
+	skel = rcu_tasks_trace_gp__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "rcu_tasks_trace_gp__open_and_load"))
+		return;
+	if (!ASSERT_OK(rcu_tasks_trace_gp__attach(skel), "rcu_tasks_trace_gp__attach"))
+		goto end;
+
+	if (test__start_subtest("success-map")) {
+		test_map_kptr_success(true);
+
+		ASSERT_OK(kern_sync_rcu_tasks_trace(skel), "sync rcu_tasks_trace");
+		ASSERT_OK(kern_sync_rcu(), "sync rcu");
+		/* Observe refcount dropping to 1 on bpf_map_free_deferred */
 		test_map_kptr_success(false);
-		/* Do test_run twice, so that we see refcount going back to 1
-		 * after we leave it in map from first iteration.
-		 */
+
+		ASSERT_OK(kern_sync_rcu_tasks_trace(skel), "sync rcu_tasks_trace");
+		ASSERT_OK(kern_sync_rcu(), "sync rcu");
+		/* Observe refcount dropping to 1 on synchronous delete elem */
 		test_map_kptr_success(true);
 	}
 
-	RUN_TESTS(map_kptr_fail);
+end:
+	rcu_tasks_trace_gp__destroy(skel);
+	return;
 }

tools/testing/selftests/bpf/progs/map_kptr.c

@@ -15,6 +15,13 @@ struct array_map {
 	__uint(max_entries, 1);
 } array_map SEC(".maps");
 
+struct pcpu_array_map {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} pcpu_array_map SEC(".maps");
+
 struct hash_map {
 	__uint(type, BPF_MAP_TYPE_HASH);
 	__type(key, int);
@@ -22,6 +29,13 @@ struct hash_map {
 	__uint(max_entries, 1);
 } hash_map SEC(".maps");
 
+struct pcpu_hash_map {
+	__uint(type, BPF_MAP_TYPE_PERCPU_HASH);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} pcpu_hash_map SEC(".maps");
+
 struct hash_malloc_map {
 	__uint(type, BPF_MAP_TYPE_HASH);
 	__type(key, int);
@@ -30,6 +44,14 @@ struct hash_malloc_map {
 	__uint(map_flags, BPF_F_NO_PREALLOC);
 } hash_malloc_map SEC(".maps");
 
+struct pcpu_hash_malloc_map {
+	__uint(type, BPF_MAP_TYPE_PERCPU_HASH);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+} pcpu_hash_malloc_map SEC(".maps");
+
 struct lru_hash_map {
 	__uint(type, BPF_MAP_TYPE_LRU_HASH);
 	__type(key, int);
@@ -37,6 +59,41 @@ struct lru_hash_map {
 	__uint(max_entries, 1);
 } lru_hash_map SEC(".maps");
 
+struct lru_pcpu_hash_map {
+	__uint(type, BPF_MAP_TYPE_LRU_PERCPU_HASH);
+	__type(key, int);
+	__type(value, struct map_value);
+	__uint(max_entries, 1);
+} lru_pcpu_hash_map SEC(".maps");
+
+struct cgrp_ls_map {
+	__uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct map_value);
+} cgrp_ls_map SEC(".maps");
+
+struct task_ls_map {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct map_value);
+} task_ls_map SEC(".maps");
+
+struct inode_ls_map {
+	__uint(type, BPF_MAP_TYPE_INODE_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct map_value);
+} inode_ls_map SEC(".maps");
+
+struct sk_ls_map {
+	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct map_value);
+} sk_ls_map SEC(".maps");
+
 #define DEFINE_MAP_OF_MAP(map_type, inner_map_type, name)       \
 	struct {                                                \
 		__uint(type, map_type);                         \
@@ -160,6 +217,58 @@ int test_map_kptr(struct __sk_buff *ctx)
 	return 0;
 }
 
+SEC("tp_btf/cgroup_mkdir")
+int BPF_PROG(test_cgrp_map_kptr, struct cgroup *cgrp, const char *path)
+{
+	struct map_value *v;
+
+	v = bpf_cgrp_storage_get(&cgrp_ls_map, cgrp, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (v)
+		test_kptr(v);
+	return 0;
+}
+
+SEC("lsm/inode_unlink")
+int BPF_PROG(test_task_map_kptr, struct inode *inode, struct dentry *victim)
+{
+	struct task_struct *task;
+	struct map_value *v;
+
+	task = bpf_get_current_task_btf();
+	if (!task)
+		return 0;
+	v = bpf_task_storage_get(&task_ls_map, task, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (v)
+		test_kptr(v);
+	return 0;
+}
+
+SEC("lsm/inode_unlink")
+int BPF_PROG(test_inode_map_kptr, struct inode *inode, struct dentry *victim)
+{
+	struct map_value *v;
+
+	v = bpf_inode_storage_get(&inode_ls_map, inode, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (v)
+		test_kptr(v);
+	return 0;
+}
+
+SEC("tc")
+int test_sk_map_kptr(struct __sk_buff *ctx)
+{
+	struct map_value *v;
+	struct bpf_sock *sk;
+
+	sk = ctx->sk;
+	if (!sk)
+		return 0;
+	v = bpf_sk_storage_get(&sk_ls_map, sk, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (v)
+		test_kptr(v);
+	return 0;
+}
+
 SEC("tc")
 int test_map_in_map_kptr(struct __sk_buff *ctx)
 {
@@ -189,106 +298,257 @@ int test_map_in_map_kptr(struct __sk_buff *ctx)
 	return 0;
 }
 
-SEC("tc")
-int test_map_kptr_ref(struct __sk_buff *ctx)
+int ref = 1;
+
+static __always_inline
+int test_map_kptr_ref_pre(struct map_value *v)
 {
 	struct prog_test_ref_kfunc *p, *p_st;
 	unsigned long arg = 0;
-	struct map_value *v;
-	int key = 0, ret;
+	int ret;
 
 	p = bpf_kfunc_call_test_acquire(&arg);
 	if (!p)
 		return 1;
+	ref++;
 
 	p_st = p->next;
-	if (p_st->cnt.refs.counter != 2) {
+	if (p_st->cnt.refs.counter != ref) {
 		ret = 2;
 		goto end;
 	}
 
-	v = bpf_map_lookup_elem(&array_map, &key);
-	if (!v) {
-		ret = 3;
-		goto end;
-	}
-
 	p = bpf_kptr_xchg(&v->ref_ptr, p);
 	if (p) {
-		ret = 4;
+		ret = 3;
 		goto end;
 	}
-	if (p_st->cnt.refs.counter != 2)
-		return 5;
+	if (p_st->cnt.refs.counter != ref)
+		return 4;
 
 	p = bpf_kfunc_call_test_kptr_get(&v->ref_ptr, 0, 0);
 	if (!p)
-		return 6;
-	if (p_st->cnt.refs.counter != 3) {
-		ret = 7;
+		return 5;
+	ref++;
+	if (p_st->cnt.refs.counter != ref) {
+		ret = 6;
 		goto end;
 	}
 	bpf_kfunc_call_test_release(p);
-	if (p_st->cnt.refs.counter != 2)
-		return 8;
+	ref--;
+	if (p_st->cnt.refs.counter != ref)
+		return 7;
 
 	p = bpf_kptr_xchg(&v->ref_ptr, NULL);
 	if (!p)
-		return 9;
+		return 8;
 	bpf_kfunc_call_test_release(p);
-	if (p_st->cnt.refs.counter != 1)
-		return 10;
+	ref--;
+	if (p_st->cnt.refs.counter != ref)
+		return 9;
 
 	p = bpf_kfunc_call_test_acquire(&arg);
 	if (!p)
-		return 11;
+		return 10;
+	ref++;
 	p = bpf_kptr_xchg(&v->ref_ptr, p);
 	if (p) {
-		ret = 12;
+		ret = 11;
 		goto end;
 	}
-	if (p_st->cnt.refs.counter != 2)
-		return 13;
+	if (p_st->cnt.refs.counter != ref)
+		return 12;
 	/* Leave in map */
 
 	return 0;
 end:
+	ref--;
 	bpf_kfunc_call_test_release(p);
 	return ret;
 }
 
-SEC("tc")
-int test_map_kptr_ref2(struct __sk_buff *ctx)
+static __always_inline
+int test_map_kptr_ref_post(struct map_value *v)
 {
 	struct prog_test_ref_kfunc *p, *p_st;
-	struct map_value *v;
-	int key = 0;
-
-	v = bpf_map_lookup_elem(&array_map, &key);
-	if (!v)
-		return 1;
 
 	p_st = v->ref_ptr;
-	if (!p_st || p_st->cnt.refs.counter != 2)
-		return 2;
+	if (!p_st || p_st->cnt.refs.counter != ref)
+		return 1;
 
 	p = bpf_kptr_xchg(&v->ref_ptr, NULL);
 	if (!p)
-		return 3;
-	if (p_st->cnt.refs.counter != 2) {
+		return 2;
+	if (p_st->cnt.refs.counter != ref) {
 		bpf_kfunc_call_test_release(p);
-		return 4;
+		return 3;
 	}
 
 	p = bpf_kptr_xchg(&v->ref_ptr, p);
 	if (p) {
 		bpf_kfunc_call_test_release(p);
-		return 5;
+		return 4;
 	}
-	if (p_st->cnt.refs.counter != 2)
-		return 6;
+	if (p_st->cnt.refs.counter != ref)
+		return 5;
+
+	return 0;
+}
+
+#define TEST(map)                            \
+	v = bpf_map_lookup_elem(&map, &key); \
+	if (!v)                              \
+		return -1;                   \
+	ret = test_map_kptr_ref_pre(v);      \
+	if (ret)                             \
+		return ret;
+
+#define TEST_PCPU(map)                                 \
+	v = bpf_map_lookup_percpu_elem(&map, &key, 0); \
+	if (!v)                                        \
+		return -1;                             \
+	ret = test_map_kptr_ref_pre(v);                \
+	if (ret)                                       \
+		return ret;
+
+SEC("tc")
+int test_map_kptr_ref1(struct __sk_buff *ctx)
+{
+	struct map_value *v, val = {};
+	int key = 0, ret;
+
+	bpf_map_update_elem(&hash_map, &key, &val, 0);
+	bpf_map_update_elem(&hash_malloc_map, &key, &val, 0);
+	bpf_map_update_elem(&lru_hash_map, &key, &val, 0);
+
+	bpf_map_update_elem(&pcpu_hash_map, &key, &val, 0);
+	bpf_map_update_elem(&pcpu_hash_malloc_map, &key, &val, 0);
+	bpf_map_update_elem(&lru_pcpu_hash_map, &key, &val, 0);
+
+	TEST(array_map);
+	TEST(hash_map);
+	TEST(hash_malloc_map);
+	TEST(lru_hash_map);
+
+	TEST_PCPU(pcpu_array_map);
+	TEST_PCPU(pcpu_hash_map);
+	TEST_PCPU(pcpu_hash_malloc_map);
+	TEST_PCPU(lru_pcpu_hash_map);
 
 	return 0;
 }
 
+#undef TEST
+#undef TEST_PCPU
+
+#define TEST(map)                            \
+	v = bpf_map_lookup_elem(&map, &key); \
+	if (!v)                              \
+		return -1;                   \
+	ret = test_map_kptr_ref_post(v);     \
+	if (ret)                             \
+		return ret;
+
+#define TEST_PCPU(map)                                 \
+	v = bpf_map_lookup_percpu_elem(&map, &key, 0); \
+	if (!v)                                        \
+		return -1;                             \
+	ret = test_map_kptr_ref_post(v);               \
+	if (ret)                                       \
+		return ret;
+
+SEC("tc")
+int test_map_kptr_ref2(struct __sk_buff *ctx)
+{
+	struct map_value *v;
+	int key = 0, ret;
+
+	TEST(array_map);
+	TEST(hash_map);
+	TEST(hash_malloc_map);
+	TEST(lru_hash_map);
+
+	TEST_PCPU(pcpu_array_map);
+	TEST_PCPU(pcpu_hash_map);
+	TEST_PCPU(pcpu_hash_malloc_map);
+	TEST_PCPU(lru_pcpu_hash_map);
+
+	return 0;
+}
+
+#undef TEST
+#undef TEST_PCPU
+
+SEC("tc")
+int test_map_kptr_ref3(struct __sk_buff *ctx)
+{
+	struct prog_test_ref_kfunc *p;
+	unsigned long sp = 0;
+
+	p = bpf_kfunc_call_test_acquire(&sp);
+	if (!p)
+		return 1;
+	ref++;
+	if (p->cnt.refs.counter != ref) {
+		bpf_kfunc_call_test_release(p);
+		return 2;
+	}
+	bpf_kfunc_call_test_release(p);
+	ref--;
+	return 0;
+}
+
+SEC("syscall")
+int test_ls_map_kptr_ref1(void *ctx)
+{
+	struct task_struct *current;
+	struct map_value *v;
+	int ret;
+
+	current = bpf_get_current_task_btf();
+	if (!current)
+		return 100;
+	v = bpf_task_storage_get(&task_ls_map, current, NULL, 0);
+	if (v)
+		return 150;
+	v = bpf_task_storage_get(&task_ls_map, current, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!v)
+		return 200;
+	return test_map_kptr_ref_pre(v);
+}
+
+SEC("syscall")
+int test_ls_map_kptr_ref2(void *ctx)
+{
+	struct task_struct *current;
+	struct map_value *v;
+	int ret;
+
+	current = bpf_get_current_task_btf();
+	if (!current)
+		return 100;
+	v = bpf_task_storage_get(&task_ls_map, current, NULL, 0);
+	if (!v)
+		return 200;
+	return test_map_kptr_ref_post(v);
+}
+
+SEC("syscall")
+int test_ls_map_kptr_ref_del(void *ctx)
+{
+	struct task_struct *current;
+	struct map_value *v;
+	int ret;
+
+	current = bpf_get_current_task_btf();
+	if (!current)
+		return 100;
+	v = bpf_task_storage_get(&task_ls_map, current, NULL, 0);
+	if (!v)
+		return 200;
+	if (!v->ref_ptr)
+		return 300;
+	return bpf_task_storage_delete(&task_ls_map, current);
+}
+
 char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/rcu_tasks_trace_gp.c

+// SPDX-License-Identifier: GPL-2.0
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+struct task_ls_map {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, int);
+} task_ls_map SEC(".maps");
+
+long gp_seq;
+
+SEC("syscall")
+int do_call_rcu_tasks_trace(void *ctx)
+{
+    struct task_struct *current;
+    int *v;
+
+    current = bpf_get_current_task_btf();
+    v = bpf_task_storage_get(&task_ls_map, current, NULL, BPF_LOCAL_STORAGE_GET_F_CREATE);
+    if (!v)
+        return 1;
+    /* Invoke call_rcu_tasks_trace */
+    return bpf_task_storage_delete(&task_ls_map, current);
+}
+
+SEC("kprobe/rcu_tasks_trace_postgp")
+int rcu_tasks_trace_postgp(void *ctx)
+{
+    __sync_add_and_fetch(&gp_seq, 1);
+    return 0;
+}
+
+char _license[] SEC("license") = "GPL";