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![Alexei Starovoitov](/assets/img/avatar_default.png)
Implement permissions as stated in uapi/linux/capability.h In order to do that the verifier allow_ptr_leaks flag is split into four flags and they are set as: env->allow_ptr_leaks = bpf_allow_ptr_leaks(); env->bypass_spec_v1 = bpf_bypass_spec_v1(); env->bypass_spec_v4 = bpf_bypass_spec_v4(); env->bpf_capable = bpf_capable(); The first three currently equivalent to perfmon_capable(), since leaking kernel pointers and reading kernel memory via side channel attacks is roughly equivalent to reading kernel memory with cap_perfmon. 'bpf_capable' enables bounded loops, precision tracking, bpf to bpf calls and other verifier features. 'allow_ptr_leaks' enable ptr leaks, ptr conversions, subtraction of pointers. 'bypass_spec_v1' disables speculative analysis in the verifier, run time mitigations in bpf array, and enables indirect variable access in bpf programs. 'bypass_spec_v4' disables emission of sanitation code by the verifier. That means that the networking BPF program loaded with CAP_BPF + CAP_NET_ADMIN will have speculative checks done by the verifier and other spectre mitigation applied. Such networking BPF program will not be able to leak kernel pointers and will not be able to access arbitrary kernel memory. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20200513230355.7858-3-alexei.starovoitov@gmail.com
289 lines
6.8 KiB
C
289 lines
6.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* queue_stack_maps.c: BPF queue and stack maps
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*
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* Copyright (c) 2018 Politecnico di Torino
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*/
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#include <linux/bpf.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/capability.h>
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#include "percpu_freelist.h"
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#define QUEUE_STACK_CREATE_FLAG_MASK \
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(BPF_F_NUMA_NODE | BPF_F_ACCESS_MASK)
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struct bpf_queue_stack {
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struct bpf_map map;
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raw_spinlock_t lock;
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u32 head, tail;
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u32 size; /* max_entries + 1 */
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char elements[] __aligned(8);
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};
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static struct bpf_queue_stack *bpf_queue_stack(struct bpf_map *map)
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{
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return container_of(map, struct bpf_queue_stack, map);
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}
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static bool queue_stack_map_is_empty(struct bpf_queue_stack *qs)
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{
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return qs->head == qs->tail;
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}
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static bool queue_stack_map_is_full(struct bpf_queue_stack *qs)
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{
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u32 head = qs->head + 1;
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if (unlikely(head >= qs->size))
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head = 0;
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return head == qs->tail;
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}
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/* Called from syscall */
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static int queue_stack_map_alloc_check(union bpf_attr *attr)
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{
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if (!bpf_capable())
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return -EPERM;
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/* check sanity of attributes */
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if (attr->max_entries == 0 || attr->key_size != 0 ||
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attr->value_size == 0 ||
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attr->map_flags & ~QUEUE_STACK_CREATE_FLAG_MASK ||
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!bpf_map_flags_access_ok(attr->map_flags))
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return -EINVAL;
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if (attr->value_size > KMALLOC_MAX_SIZE)
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/* if value_size is bigger, the user space won't be able to
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* access the elements.
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*/
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return -E2BIG;
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return 0;
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}
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static struct bpf_map *queue_stack_map_alloc(union bpf_attr *attr)
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{
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int ret, numa_node = bpf_map_attr_numa_node(attr);
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struct bpf_map_memory mem = {0};
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struct bpf_queue_stack *qs;
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u64 size, queue_size, cost;
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size = (u64) attr->max_entries + 1;
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cost = queue_size = sizeof(*qs) + size * attr->value_size;
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ret = bpf_map_charge_init(&mem, cost);
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if (ret < 0)
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return ERR_PTR(ret);
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qs = bpf_map_area_alloc(queue_size, numa_node);
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if (!qs) {
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bpf_map_charge_finish(&mem);
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return ERR_PTR(-ENOMEM);
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}
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memset(qs, 0, sizeof(*qs));
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bpf_map_init_from_attr(&qs->map, attr);
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bpf_map_charge_move(&qs->map.memory, &mem);
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qs->size = size;
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raw_spin_lock_init(&qs->lock);
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return &qs->map;
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}
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/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
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static void queue_stack_map_free(struct bpf_map *map)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
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* so the programs (can be more than one that used this map) were
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* disconnected from events. Wait for outstanding critical sections in
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* these programs to complete
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*/
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synchronize_rcu();
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bpf_map_area_free(qs);
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}
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static int __queue_map_get(struct bpf_map *map, void *value, bool delete)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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unsigned long flags;
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int err = 0;
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void *ptr;
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raw_spin_lock_irqsave(&qs->lock, flags);
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if (queue_stack_map_is_empty(qs)) {
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memset(value, 0, qs->map.value_size);
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err = -ENOENT;
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goto out;
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}
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ptr = &qs->elements[qs->tail * qs->map.value_size];
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memcpy(value, ptr, qs->map.value_size);
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if (delete) {
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if (unlikely(++qs->tail >= qs->size))
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qs->tail = 0;
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}
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out:
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raw_spin_unlock_irqrestore(&qs->lock, flags);
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return err;
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}
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static int __stack_map_get(struct bpf_map *map, void *value, bool delete)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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unsigned long flags;
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int err = 0;
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void *ptr;
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u32 index;
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raw_spin_lock_irqsave(&qs->lock, flags);
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if (queue_stack_map_is_empty(qs)) {
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memset(value, 0, qs->map.value_size);
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err = -ENOENT;
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goto out;
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}
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index = qs->head - 1;
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if (unlikely(index >= qs->size))
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index = qs->size - 1;
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ptr = &qs->elements[index * qs->map.value_size];
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memcpy(value, ptr, qs->map.value_size);
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if (delete)
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qs->head = index;
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out:
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raw_spin_unlock_irqrestore(&qs->lock, flags);
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return err;
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}
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/* Called from syscall or from eBPF program */
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static int queue_map_peek_elem(struct bpf_map *map, void *value)
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{
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return __queue_map_get(map, value, false);
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}
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/* Called from syscall or from eBPF program */
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static int stack_map_peek_elem(struct bpf_map *map, void *value)
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{
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return __stack_map_get(map, value, false);
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}
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/* Called from syscall or from eBPF program */
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static int queue_map_pop_elem(struct bpf_map *map, void *value)
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{
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return __queue_map_get(map, value, true);
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}
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/* Called from syscall or from eBPF program */
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static int stack_map_pop_elem(struct bpf_map *map, void *value)
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{
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return __stack_map_get(map, value, true);
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}
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/* Called from syscall or from eBPF program */
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static int queue_stack_map_push_elem(struct bpf_map *map, void *value,
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u64 flags)
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{
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struct bpf_queue_stack *qs = bpf_queue_stack(map);
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unsigned long irq_flags;
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int err = 0;
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void *dst;
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/* BPF_EXIST is used to force making room for a new element in case the
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* map is full
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*/
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bool replace = (flags & BPF_EXIST);
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/* Check supported flags for queue and stack maps */
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if (flags & BPF_NOEXIST || flags > BPF_EXIST)
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return -EINVAL;
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raw_spin_lock_irqsave(&qs->lock, irq_flags);
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if (queue_stack_map_is_full(qs)) {
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if (!replace) {
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err = -E2BIG;
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goto out;
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}
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/* advance tail pointer to overwrite oldest element */
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if (unlikely(++qs->tail >= qs->size))
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qs->tail = 0;
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}
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dst = &qs->elements[qs->head * qs->map.value_size];
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memcpy(dst, value, qs->map.value_size);
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if (unlikely(++qs->head >= qs->size))
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qs->head = 0;
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out:
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raw_spin_unlock_irqrestore(&qs->lock, irq_flags);
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return err;
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}
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/* Called from syscall or from eBPF program */
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static void *queue_stack_map_lookup_elem(struct bpf_map *map, void *key)
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{
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return NULL;
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}
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/* Called from syscall or from eBPF program */
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static int queue_stack_map_update_elem(struct bpf_map *map, void *key,
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void *value, u64 flags)
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{
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return -EINVAL;
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}
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/* Called from syscall or from eBPF program */
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static int queue_stack_map_delete_elem(struct bpf_map *map, void *key)
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{
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return -EINVAL;
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}
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/* Called from syscall */
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static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
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void *next_key)
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{
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return -EINVAL;
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}
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const struct bpf_map_ops queue_map_ops = {
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.map_alloc_check = queue_stack_map_alloc_check,
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.map_alloc = queue_stack_map_alloc,
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.map_free = queue_stack_map_free,
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.map_lookup_elem = queue_stack_map_lookup_elem,
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.map_update_elem = queue_stack_map_update_elem,
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.map_delete_elem = queue_stack_map_delete_elem,
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.map_push_elem = queue_stack_map_push_elem,
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.map_pop_elem = queue_map_pop_elem,
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.map_peek_elem = queue_map_peek_elem,
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.map_get_next_key = queue_stack_map_get_next_key,
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};
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const struct bpf_map_ops stack_map_ops = {
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.map_alloc_check = queue_stack_map_alloc_check,
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.map_alloc = queue_stack_map_alloc,
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.map_free = queue_stack_map_free,
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.map_lookup_elem = queue_stack_map_lookup_elem,
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.map_update_elem = queue_stack_map_update_elem,
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.map_delete_elem = queue_stack_map_delete_elem,
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.map_push_elem = queue_stack_map_push_elem,
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.map_pop_elem = stack_map_pop_elem,
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.map_peek_elem = stack_map_peek_elem,
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.map_get_next_key = queue_stack_map_get_next_key,
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};
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