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![Alexei Starovoitov](/assets/img/avatar_default.png)
add optional attributes for BPF_PROG_LOAD syscall: union bpf_attr { struct { ... __u32 log_level; /* verbosity level of eBPF verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied 'char *buffer' */ }; }; when log_level > 0 the verifier will return its verification log in the user supplied buffer 'log_buf' which can be used by program author to analyze why verifier rejected given program. 'Understanding eBPF verifier messages' section of Documentation/networking/filter.txt provides several examples of these messages, like the program: BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), BPF_LD_MAP_FD(BPF_REG_1, 0), BPF_CALL_FUNC(BPF_FUNC_map_lookup_elem), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), BPF_ST_MEM(BPF_DW, BPF_REG_0, 4, 0), BPF_EXIT_INSN(), will be rejected with the following multi-line message in log_buf: 0: (7a) *(u64 *)(r10 -8) = 0 1: (bf) r2 = r10 2: (07) r2 += -8 3: (b7) r1 = 0 4: (85) call 1 5: (15) if r0 == 0x0 goto pc+1 R0=map_ptr R10=fp 6: (7a) *(u64 *)(r0 +4) = 0 misaligned access off 4 size 8 The format of the output can change at any time as verifier evolves. Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
606 lines
13 KiB
C
606 lines
13 KiB
C
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/bpf.h>
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#include <linux/syscalls.h>
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#include <linux/slab.h>
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#include <linux/anon_inodes.h>
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#include <linux/file.h>
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#include <linux/license.h>
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#include <linux/filter.h>
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static LIST_HEAD(bpf_map_types);
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static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
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{
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struct bpf_map_type_list *tl;
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struct bpf_map *map;
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list_for_each_entry(tl, &bpf_map_types, list_node) {
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if (tl->type == attr->map_type) {
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map = tl->ops->map_alloc(attr);
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if (IS_ERR(map))
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return map;
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map->ops = tl->ops;
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map->map_type = attr->map_type;
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return map;
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}
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}
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return ERR_PTR(-EINVAL);
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}
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/* boot time registration of different map implementations */
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void bpf_register_map_type(struct bpf_map_type_list *tl)
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{
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list_add(&tl->list_node, &bpf_map_types);
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}
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/* called from workqueue */
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static void bpf_map_free_deferred(struct work_struct *work)
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{
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struct bpf_map *map = container_of(work, struct bpf_map, work);
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/* implementation dependent freeing */
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map->ops->map_free(map);
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}
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/* decrement map refcnt and schedule it for freeing via workqueue
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* (unrelying map implementation ops->map_free() might sleep)
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*/
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void bpf_map_put(struct bpf_map *map)
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{
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if (atomic_dec_and_test(&map->refcnt)) {
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INIT_WORK(&map->work, bpf_map_free_deferred);
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schedule_work(&map->work);
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}
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}
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static int bpf_map_release(struct inode *inode, struct file *filp)
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{
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struct bpf_map *map = filp->private_data;
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bpf_map_put(map);
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return 0;
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}
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static const struct file_operations bpf_map_fops = {
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.release = bpf_map_release,
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};
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/* helper macro to check that unused fields 'union bpf_attr' are zero */
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#define CHECK_ATTR(CMD) \
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memchr_inv((void *) &attr->CMD##_LAST_FIELD + \
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sizeof(attr->CMD##_LAST_FIELD), 0, \
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sizeof(*attr) - \
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offsetof(union bpf_attr, CMD##_LAST_FIELD) - \
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sizeof(attr->CMD##_LAST_FIELD)) != NULL
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#define BPF_MAP_CREATE_LAST_FIELD max_entries
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/* called via syscall */
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static int map_create(union bpf_attr *attr)
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{
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struct bpf_map *map;
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int err;
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err = CHECK_ATTR(BPF_MAP_CREATE);
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if (err)
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return -EINVAL;
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/* find map type and init map: hashtable vs rbtree vs bloom vs ... */
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map = find_and_alloc_map(attr);
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if (IS_ERR(map))
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return PTR_ERR(map);
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atomic_set(&map->refcnt, 1);
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err = anon_inode_getfd("bpf-map", &bpf_map_fops, map, O_RDWR | O_CLOEXEC);
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if (err < 0)
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/* failed to allocate fd */
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goto free_map;
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return err;
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free_map:
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map->ops->map_free(map);
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return err;
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}
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/* if error is returned, fd is released.
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* On success caller should complete fd access with matching fdput()
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*/
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struct bpf_map *bpf_map_get(struct fd f)
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{
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struct bpf_map *map;
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if (!f.file)
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return ERR_PTR(-EBADF);
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if (f.file->f_op != &bpf_map_fops) {
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fdput(f);
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return ERR_PTR(-EINVAL);
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}
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map = f.file->private_data;
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return map;
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}
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/* helper to convert user pointers passed inside __aligned_u64 fields */
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static void __user *u64_to_ptr(__u64 val)
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{
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return (void __user *) (unsigned long) val;
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}
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/* last field in 'union bpf_attr' used by this command */
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#define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value
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static int map_lookup_elem(union bpf_attr *attr)
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{
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void __user *ukey = u64_to_ptr(attr->key);
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void __user *uvalue = u64_to_ptr(attr->value);
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int ufd = attr->map_fd;
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struct fd f = fdget(ufd);
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struct bpf_map *map;
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void *key, *value;
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int err;
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if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
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return -EINVAL;
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map = bpf_map_get(f);
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if (IS_ERR(map))
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return PTR_ERR(map);
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err = -ENOMEM;
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key = kmalloc(map->key_size, GFP_USER);
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if (!key)
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goto err_put;
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err = -EFAULT;
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if (copy_from_user(key, ukey, map->key_size) != 0)
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goto free_key;
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err = -ESRCH;
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rcu_read_lock();
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value = map->ops->map_lookup_elem(map, key);
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if (!value)
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goto err_unlock;
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err = -EFAULT;
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if (copy_to_user(uvalue, value, map->value_size) != 0)
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goto err_unlock;
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err = 0;
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err_unlock:
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rcu_read_unlock();
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free_key:
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kfree(key);
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err_put:
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fdput(f);
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return err;
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}
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#define BPF_MAP_UPDATE_ELEM_LAST_FIELD value
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static int map_update_elem(union bpf_attr *attr)
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{
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void __user *ukey = u64_to_ptr(attr->key);
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void __user *uvalue = u64_to_ptr(attr->value);
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int ufd = attr->map_fd;
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struct fd f = fdget(ufd);
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struct bpf_map *map;
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void *key, *value;
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int err;
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if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
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return -EINVAL;
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map = bpf_map_get(f);
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if (IS_ERR(map))
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return PTR_ERR(map);
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err = -ENOMEM;
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key = kmalloc(map->key_size, GFP_USER);
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if (!key)
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goto err_put;
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err = -EFAULT;
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if (copy_from_user(key, ukey, map->key_size) != 0)
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goto free_key;
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err = -ENOMEM;
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value = kmalloc(map->value_size, GFP_USER);
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if (!value)
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goto free_key;
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err = -EFAULT;
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if (copy_from_user(value, uvalue, map->value_size) != 0)
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goto free_value;
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/* eBPF program that use maps are running under rcu_read_lock(),
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* therefore all map accessors rely on this fact, so do the same here
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*/
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rcu_read_lock();
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err = map->ops->map_update_elem(map, key, value);
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rcu_read_unlock();
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free_value:
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kfree(value);
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free_key:
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kfree(key);
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err_put:
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fdput(f);
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return err;
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}
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#define BPF_MAP_DELETE_ELEM_LAST_FIELD key
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static int map_delete_elem(union bpf_attr *attr)
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{
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void __user *ukey = u64_to_ptr(attr->key);
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int ufd = attr->map_fd;
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struct fd f = fdget(ufd);
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struct bpf_map *map;
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void *key;
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int err;
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if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
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return -EINVAL;
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map = bpf_map_get(f);
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if (IS_ERR(map))
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return PTR_ERR(map);
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err = -ENOMEM;
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key = kmalloc(map->key_size, GFP_USER);
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if (!key)
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goto err_put;
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err = -EFAULT;
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if (copy_from_user(key, ukey, map->key_size) != 0)
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goto free_key;
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rcu_read_lock();
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err = map->ops->map_delete_elem(map, key);
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rcu_read_unlock();
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free_key:
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kfree(key);
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err_put:
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fdput(f);
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return err;
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}
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/* last field in 'union bpf_attr' used by this command */
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#define BPF_MAP_GET_NEXT_KEY_LAST_FIELD next_key
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static int map_get_next_key(union bpf_attr *attr)
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{
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void __user *ukey = u64_to_ptr(attr->key);
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void __user *unext_key = u64_to_ptr(attr->next_key);
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int ufd = attr->map_fd;
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struct fd f = fdget(ufd);
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struct bpf_map *map;
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void *key, *next_key;
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int err;
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if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
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return -EINVAL;
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map = bpf_map_get(f);
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if (IS_ERR(map))
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return PTR_ERR(map);
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err = -ENOMEM;
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key = kmalloc(map->key_size, GFP_USER);
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if (!key)
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goto err_put;
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err = -EFAULT;
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if (copy_from_user(key, ukey, map->key_size) != 0)
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goto free_key;
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err = -ENOMEM;
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next_key = kmalloc(map->key_size, GFP_USER);
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if (!next_key)
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goto free_key;
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rcu_read_lock();
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err = map->ops->map_get_next_key(map, key, next_key);
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rcu_read_unlock();
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if (err)
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goto free_next_key;
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err = -EFAULT;
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if (copy_to_user(unext_key, next_key, map->key_size) != 0)
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goto free_next_key;
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err = 0;
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free_next_key:
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kfree(next_key);
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free_key:
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kfree(key);
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err_put:
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fdput(f);
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return err;
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}
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static LIST_HEAD(bpf_prog_types);
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static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
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{
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struct bpf_prog_type_list *tl;
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list_for_each_entry(tl, &bpf_prog_types, list_node) {
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if (tl->type == type) {
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prog->aux->ops = tl->ops;
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prog->aux->prog_type = type;
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return 0;
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}
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}
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return -EINVAL;
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}
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void bpf_register_prog_type(struct bpf_prog_type_list *tl)
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{
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list_add(&tl->list_node, &bpf_prog_types);
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}
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/* fixup insn->imm field of bpf_call instructions:
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* if (insn->imm == BPF_FUNC_map_lookup_elem)
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* insn->imm = bpf_map_lookup_elem - __bpf_call_base;
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* else if (insn->imm == BPF_FUNC_map_update_elem)
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* insn->imm = bpf_map_update_elem - __bpf_call_base;
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* else ...
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*
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* this function is called after eBPF program passed verification
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*/
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static void fixup_bpf_calls(struct bpf_prog *prog)
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{
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const struct bpf_func_proto *fn;
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int i;
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for (i = 0; i < prog->len; i++) {
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struct bpf_insn *insn = &prog->insnsi[i];
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if (insn->code == (BPF_JMP | BPF_CALL)) {
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/* we reach here when program has bpf_call instructions
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* and it passed bpf_check(), means that
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* ops->get_func_proto must have been supplied, check it
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*/
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BUG_ON(!prog->aux->ops->get_func_proto);
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fn = prog->aux->ops->get_func_proto(insn->imm);
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/* all functions that have prototype and verifier allowed
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* programs to call them, must be real in-kernel functions
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*/
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BUG_ON(!fn->func);
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insn->imm = fn->func - __bpf_call_base;
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}
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}
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}
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/* drop refcnt on maps used by eBPF program and free auxilary data */
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static void free_used_maps(struct bpf_prog_aux *aux)
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{
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int i;
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for (i = 0; i < aux->used_map_cnt; i++)
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bpf_map_put(aux->used_maps[i]);
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kfree(aux->used_maps);
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}
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void bpf_prog_put(struct bpf_prog *prog)
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{
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if (atomic_dec_and_test(&prog->aux->refcnt)) {
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free_used_maps(prog->aux);
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bpf_prog_free(prog);
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}
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}
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static int bpf_prog_release(struct inode *inode, struct file *filp)
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{
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struct bpf_prog *prog = filp->private_data;
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bpf_prog_put(prog);
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return 0;
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}
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static const struct file_operations bpf_prog_fops = {
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.release = bpf_prog_release,
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};
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static struct bpf_prog *get_prog(struct fd f)
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{
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struct bpf_prog *prog;
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if (!f.file)
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return ERR_PTR(-EBADF);
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if (f.file->f_op != &bpf_prog_fops) {
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fdput(f);
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return ERR_PTR(-EINVAL);
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}
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prog = f.file->private_data;
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return prog;
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}
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/* called by sockets/tracing/seccomp before attaching program to an event
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* pairs with bpf_prog_put()
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*/
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struct bpf_prog *bpf_prog_get(u32 ufd)
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{
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struct fd f = fdget(ufd);
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struct bpf_prog *prog;
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prog = get_prog(f);
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if (IS_ERR(prog))
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return prog;
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atomic_inc(&prog->aux->refcnt);
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fdput(f);
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return prog;
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}
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/* last field in 'union bpf_attr' used by this command */
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#define BPF_PROG_LOAD_LAST_FIELD log_buf
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static int bpf_prog_load(union bpf_attr *attr)
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{
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enum bpf_prog_type type = attr->prog_type;
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struct bpf_prog *prog;
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int err;
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char license[128];
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bool is_gpl;
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if (CHECK_ATTR(BPF_PROG_LOAD))
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return -EINVAL;
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/* copy eBPF program license from user space */
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if (strncpy_from_user(license, u64_to_ptr(attr->license),
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sizeof(license) - 1) < 0)
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return -EFAULT;
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license[sizeof(license) - 1] = 0;
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/* eBPF programs must be GPL compatible to use GPL-ed functions */
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is_gpl = license_is_gpl_compatible(license);
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if (attr->insn_cnt >= BPF_MAXINSNS)
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return -EINVAL;
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/* plain bpf_prog allocation */
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prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
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if (!prog)
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return -ENOMEM;
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prog->len = attr->insn_cnt;
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err = -EFAULT;
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if (copy_from_user(prog->insns, u64_to_ptr(attr->insns),
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prog->len * sizeof(struct bpf_insn)) != 0)
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goto free_prog;
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prog->orig_prog = NULL;
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prog->jited = false;
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atomic_set(&prog->aux->refcnt, 1);
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prog->aux->is_gpl_compatible = is_gpl;
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/* find program type: socket_filter vs tracing_filter */
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err = find_prog_type(type, prog);
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if (err < 0)
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goto free_prog;
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/* run eBPF verifier */
|
|
err = bpf_check(prog, attr);
|
|
|
|
if (err < 0)
|
|
goto free_used_maps;
|
|
|
|
/* fixup BPF_CALL->imm field */
|
|
fixup_bpf_calls(prog);
|
|
|
|
/* eBPF program is ready to be JITed */
|
|
bpf_prog_select_runtime(prog);
|
|
|
|
err = anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog, O_RDWR | O_CLOEXEC);
|
|
|
|
if (err < 0)
|
|
/* failed to allocate fd */
|
|
goto free_used_maps;
|
|
|
|
return err;
|
|
|
|
free_used_maps:
|
|
free_used_maps(prog->aux);
|
|
free_prog:
|
|
bpf_prog_free(prog);
|
|
return err;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
|
|
{
|
|
union bpf_attr attr = {};
|
|
int err;
|
|
|
|
/* the syscall is limited to root temporarily. This restriction will be
|
|
* lifted when security audit is clean. Note that eBPF+tracing must have
|
|
* this restriction, since it may pass kernel data to user space
|
|
*/
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
|
|
if (!access_ok(VERIFY_READ, uattr, 1))
|
|
return -EFAULT;
|
|
|
|
if (size > PAGE_SIZE) /* silly large */
|
|
return -E2BIG;
|
|
|
|
/* If we're handed a bigger struct than we know of,
|
|
* ensure all the unknown bits are 0 - i.e. new
|
|
* user-space does not rely on any kernel feature
|
|
* extensions we dont know about yet.
|
|
*/
|
|
if (size > sizeof(attr)) {
|
|
unsigned char __user *addr;
|
|
unsigned char __user *end;
|
|
unsigned char val;
|
|
|
|
addr = (void __user *)uattr + sizeof(attr);
|
|
end = (void __user *)uattr + size;
|
|
|
|
for (; addr < end; addr++) {
|
|
err = get_user(val, addr);
|
|
if (err)
|
|
return err;
|
|
if (val)
|
|
return -E2BIG;
|
|
}
|
|
size = sizeof(attr);
|
|
}
|
|
|
|
/* copy attributes from user space, may be less than sizeof(bpf_attr) */
|
|
if (copy_from_user(&attr, uattr, size) != 0)
|
|
return -EFAULT;
|
|
|
|
switch (cmd) {
|
|
case BPF_MAP_CREATE:
|
|
err = map_create(&attr);
|
|
break;
|
|
case BPF_MAP_LOOKUP_ELEM:
|
|
err = map_lookup_elem(&attr);
|
|
break;
|
|
case BPF_MAP_UPDATE_ELEM:
|
|
err = map_update_elem(&attr);
|
|
break;
|
|
case BPF_MAP_DELETE_ELEM:
|
|
err = map_delete_elem(&attr);
|
|
break;
|
|
case BPF_MAP_GET_NEXT_KEY:
|
|
err = map_get_next_key(&attr);
|
|
break;
|
|
case BPF_PROG_LOAD:
|
|
err = bpf_prog_load(&attr);
|
|
break;
|
|
default:
|
|
err = -EINVAL;
|
|
break;
|
|
}
|
|
|
|
return err;
|
|
}
|