diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 8061a43..052580c 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -1,8 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2016 Facebook
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of version 2 of the GNU General Public
- * License as published by the Free Software Foundation.
  */
 #include <linux/bpf.h>
 #include <linux/jhash.h>
@@ -44,7 +41,7 @@
 	struct stack_map_irq_work *work;
 
 	work = container_of(entry, struct stack_map_irq_work, irq_work);
-	up_read(work->sem);
+	up_read_non_owner(work->sem);
 	work->sem = NULL;
 }
 
@@ -89,6 +86,7 @@
 {
 	u32 value_size = attr->value_size;
 	struct bpf_stack_map *smap;
+	struct bpf_map_memory mem;
 	u64 cost, n_buckets;
 	int err;
 
@@ -116,40 +114,37 @@
 	n_buckets = roundup_pow_of_two(attr->max_entries);
 
 	cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
-	if (cost >= U32_MAX - PAGE_SIZE)
-		return ERR_PTR(-E2BIG);
+	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
+	err = bpf_map_charge_init(&mem, cost);
+	if (err)
+		return ERR_PTR(err);
 
 	smap = bpf_map_area_alloc(cost, bpf_map_attr_numa_node(attr));
-	if (!smap)
+	if (!smap) {
+		bpf_map_charge_finish(&mem);
 		return ERR_PTR(-ENOMEM);
-
-	err = -E2BIG;
-	cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
-	if (cost >= U32_MAX - PAGE_SIZE)
-		goto free_smap;
+	}
 
 	bpf_map_init_from_attr(&smap->map, attr);
 	smap->map.value_size = value_size;
 	smap->n_buckets = n_buckets;
-	smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
-
-	err = bpf_map_precharge_memlock(smap->map.pages);
-	if (err)
-		goto free_smap;
 
 	err = get_callchain_buffers(sysctl_perf_event_max_stack);
 	if (err)
-		goto free_smap;
+		goto free_charge;
 
 	err = prealloc_elems_and_freelist(smap);
 	if (err)
 		goto put_buffers;
 
+	bpf_map_charge_move(&smap->map.memory, &mem);
+
 	return &smap->map;
 
 put_buffers:
 	put_callchain_buffers();
-free_smap:
+free_charge:
+	bpf_map_charge_finish(&mem);
 	bpf_map_area_free(smap);
 	return ERR_PTR(err);
 }
@@ -180,11 +175,14 @@
 
 		if (nhdr->n_type == BPF_BUILD_ID &&
 		    nhdr->n_namesz == sizeof("GNU") &&
-		    nhdr->n_descsz == BPF_BUILD_ID_SIZE) {
+		    nhdr->n_descsz > 0 &&
+		    nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {
 			memcpy(build_id,
 			       note_start + note_offs +
 			       ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
-			       BPF_BUILD_ID_SIZE);
+			       nhdr->n_descsz);
+			memset(build_id + nhdr->n_descsz, 0,
+			       BPF_BUILD_ID_SIZE - nhdr->n_descsz);
 			return 0;
 		}
 		new_offs = note_offs + sizeof(Elf32_Nhdr) +
@@ -260,7 +258,7 @@
 		return -EFAULT;	/* page not mapped */
 
 	ret = -EINVAL;
-	page_addr = page_address(page);
+	page_addr = kmap_atomic(page);
 	ehdr = (Elf32_Ehdr *)page_addr;
 
 	/* compare magic x7f "ELF" */
@@ -276,6 +274,7 @@
 	else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
 		ret = stack_map_get_build_id_64(page_addr, build_id);
 out:
+	kunmap_atomic(page_addr);
 	put_page(page);
 	return ret;
 }
@@ -310,6 +309,7 @@
 		for (i = 0; i < trace_nr; i++) {
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 			id_offs[i].ip = ips[i];
+			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 		}
 		return;
 	}
@@ -320,6 +320,7 @@
 			/* per entry fall back to ips */
 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
 			id_offs[i].ip = ips[i];
+			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
 			continue;
 		}
 		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
@@ -332,6 +333,12 @@
 	} else {
 		work->sem = &current->mm->mmap_sem;
 		irq_work_queue(&work->irq_work);
+		/*
+		 * The irq_work will release the mmap_sem with
+		 * up_read_non_owner(). The rwsem_release() is called
+		 * here to release the lock from lockdep's perspective.
+		 */
+		rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
 	}
 }
 
@@ -505,7 +512,7 @@
 /* Called from eBPF program */
 static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
 {
-	return NULL;
+	return ERR_PTR(-EOPNOTSUPP);
 }
 
 /* Called from syscall */
@@ -600,7 +607,7 @@
 	put_callchain_buffers();
 }
 
-const struct bpf_map_ops stack_map_ops = {
+const struct bpf_map_ops stack_trace_map_ops = {
 	.map_alloc = stack_map_alloc,
 	.map_free = stack_map_free,
 	.map_get_next_key = stack_map_get_next_key,