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bpf: Pass map file to .map_update_batch directly

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Currently bpf_map_do_batch() first invokes fdget(batch.map_fd) to get
the target map file, then it invokes generic_map_update_batch() to do
batch update. generic_map_update_batch() will get the target map file
by using fdget(batch.map_fd) again and pass it to bpf_map_update_value().

The problem is map file returned by the second fdget() may be NULL or a
totally different file compared by map file in bpf_map_do_batch(). The
reason is that the first fdget() only guarantees the liveness of struct
file instead of file descriptor and the file description may be released
by concurrent close() through pick_file().

It doesn't incur any problem as for now, because maps with batch update
support don't use map file in .map_fd_get_ptr() ops. But it is better to
fix the potential access of an invalid map file.

Using __bpf_map_get() again in generic_map_update_batch() can not fix
the problem, because batch.map_fd may be closed and reopened, and the
returned map file may be different with map file got in
bpf_map_do_batch(), so just passing the map file directly to
.map_update_batch() in bpf_map_do_batch().

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221116075059.1551277-1-houtao@huaweicloud.com
This commit is contained in:
Hou Tao 2022-11-16 15:50:58 +08:00 committed by Daniel Borkmann
parent 383f1a8df8
commit 3af43ba4c6
2 changed files with 17 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/bpf.h
View File

@ -85,7 +85,8 @@ struct bpf_map_ops {
int (*map_lookup_and_delete_batch)(struct bpf_map *map,
const union bpf_attr *attr,
union bpf_attr __user *uattr);
int (*map_update_batch)(struct bpf_map *map, const union bpf_attr *attr,
int (*map_update_batch)(struct bpf_map *map, struct file *map_file,
const union bpf_attr *attr,
union bpf_attr __user *uattr);
int (*map_delete_batch)(struct bpf_map *map, const union bpf_attr *attr,
union bpf_attr __user *uattr);
@ -1789,7 +1790,7 @@ void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr);
int generic_map_lookup_batch(struct bpf_map *map,
const union bpf_attr *attr,
union bpf_attr __user *uattr);
int generic_map_update_batch(struct bpf_map *map,
int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
const union bpf_attr *attr,
union bpf_attr __user *uattr);
int generic_map_delete_batch(struct bpf_map *map,

32
kernel/bpf/syscall.c
View File

@ -175,8 +175,8 @@ static void maybe_wait_bpf_programs(struct bpf_map *map)
synchronize_rcu();
}
static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key,
void *value, __u64 flags)
static int bpf_map_update_value(struct bpf_map *map, struct file *map_file,
void *key, void *value, __u64 flags)
{
int err;
@ -190,7 +190,7 @@ static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key,
map->map_type == BPF_MAP_TYPE_SOCKMAP) {
return sock_map_update_elem_sys(map, key, value, flags);
} else if (IS_FD_PROG_ARRAY(map)) {
return bpf_fd_array_map_update_elem(map, f.file, key, value,
return bpf_fd_array_map_update_elem(map, map_file, key, value,
flags);
}
@ -205,12 +205,12 @@ static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key,
flags);
} else if (IS_FD_ARRAY(map)) {
rcu_read_lock();
err = bpf_fd_array_map_update_elem(map, f.file, key, value,
err = bpf_fd_array_map_update_elem(map, map_file, key, value,
flags);
rcu_read_unlock();
} else if (map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
rcu_read_lock();
err = bpf_fd_htab_map_update_elem(map, f.file, key, value,
err = bpf_fd_htab_map_update_elem(map, map_file, key, value,
flags);
rcu_read_unlock();
} else if (map->map_type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY) {
@ -1410,7 +1410,7 @@ static int map_update_elem(union bpf_attr *attr, bpfptr_t uattr)
goto free_key;
}
err = bpf_map_update_value(map, f, key, value, attr->flags);
err = bpf_map_update_value(map, f.file, key, value, attr->flags);
kvfree(value);
free_key:
@ -1596,16 +1596,14 @@ int generic_map_delete_batch(struct bpf_map *map,
return err;
}
int generic_map_update_batch(struct bpf_map *map,
int generic_map_update_batch(struct bpf_map *map, struct file *map_file,
const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
void __user *values = u64_to_user_ptr(attr->batch.values);
void __user *keys = u64_to_user_ptr(attr->batch.keys);
u32 value_size, cp, max_count;
int ufd = attr->batch.map_fd;
void *key, *value;
struct fd f;
int err = 0;
if (attr->batch.elem_flags & ~BPF_F_LOCK)
@ -1632,7 +1630,6 @@ int generic_map_update_batch(struct bpf_map *map,
return -ENOMEM;
}
f = fdget(ufd); /* bpf_map_do_batch() guarantees ufd is valid */
for (cp = 0; cp < max_count; cp++) {
err = -EFAULT;
if (copy_from_user(key, keys + cp * map->key_size,
@ -1640,7 +1637,7 @@ int generic_map_update_batch(struct bpf_map *map,
copy_from_user(value, values + cp * value_size, value_size))
break;
err = bpf_map_update_value(map, f, key, value,
err = bpf_map_update_value(map, map_file, key, value,
attr->batch.elem_flags);
if (err)
@ -1653,7 +1650,6 @@ int generic_map_update_batch(struct bpf_map *map,
kvfree(value);
kvfree(key);
fdput(f);
return err;
}
@ -4446,13 +4442,13 @@ put_file:
#define BPF_MAP_BATCH_LAST_FIELD batch.flags
#define BPF_DO_BATCH(fn) \
#define BPF_DO_BATCH(fn, ...) \
do { \
if (!fn) { \
err = -ENOTSUPP; \
goto err_put; \
} \
err = fn(map, attr, uattr); \
err = fn(__VA_ARGS__); \
} while (0)
static int bpf_map_do_batch(const union bpf_attr *attr,
@ -4486,13 +4482,13 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
}
if (cmd == BPF_MAP_LOOKUP_BATCH)
BPF_DO_BATCH(map->ops->map_lookup_batch);
BPF_DO_BATCH(map->ops->map_lookup_batch, map, attr, uattr);
else if (cmd == BPF_MAP_LOOKUP_AND_DELETE_BATCH)
BPF_DO_BATCH(map->ops->map_lookup_and_delete_batch);
BPF_DO_BATCH(map->ops->map_lookup_and_delete_batch, map, attr, uattr);
else if (cmd == BPF_MAP_UPDATE_BATCH)
BPF_DO_BATCH(map->ops->map_update_batch);
BPF_DO_BATCH(map->ops->map_update_batch, map, f.file, attr, uattr);
else
BPF_DO_BATCH(map->ops->map_delete_batch);
BPF_DO_BATCH(map->ops->map_delete_batch, map, attr, uattr);
err_put:
if (has_write)
bpf_map_write_active_dec(map);