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Merge branch 'bpf: Build with -Wcast-function-type' 

Kees Cook says:

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

Hi,

In order to keep ahead of cases in the kernel where Control Flow Integrity
(CFI) may trip over function call casts, enabling -Wcast-function-type
is helpful. To that end, replace BPF_CAST_CALL() as it triggers warnings
with this option and is now one of the last places in the kernel in need
of fixing.

Thanks,

-Kees

v2:
- rebase to bpf-next
- add acks
v1: https://lore.kernel.org/lkml/20210927182700.2980499-1-keescook@chromium.org
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2021-09-28 16:27:18 -07:00
parent 09710d82c0 102acbacfd
commit 72e1781a5d
7 changed files with 27 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/bpf.h
View File

@ -48,6 +48,7 @@ extern struct idr btf_idr;
extern spinlock_t btf_idr_lock;
extern struct kobject *btf_kobj;
typedef u64 (*bpf_callback_t)(u64, u64, u64, u64, u64);
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
struct bpf_iter_aux_info *aux);
typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
@ -142,7 +143,8 @@ struct bpf_map_ops {
int (*map_set_for_each_callback_args)(struct bpf_verifier_env *env,
struct bpf_func_state *caller,
struct bpf_func_state *callee);
int (*map_for_each_callback)(struct bpf_map *map, void *callback_fn,
int (*map_for_each_callback)(struct bpf_map *map,
bpf_callback_t callback_fn,
void *callback_ctx, u64 flags);
/* BTF name and id of struct allocated by map_alloc */

7
include/linux/filter.h
View File

@ -360,10 +360,9 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
.off = 0, \
.imm = TGT })
/* Function call */
/* Convert function address to BPF immediate */
#define BPF_CAST_CALL(x) \
((u64 (*)(u64, u64, u64, u64, u64))(x))
#define BPF_CALL_IMM(x) ((void *)(x) - (void *)__bpf_call_base)
#define BPF_EMIT_CALL(FUNC) \
((struct bpf_insn) { \
@ -371,7 +370,7 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
.dst_reg = 0, \
.src_reg = 0, \
.off = 0, \
.imm = ((FUNC) - __bpf_call_base) })
.imm = BPF_CALL_IMM(FUNC) })
/* Raw code statement block */

7
kernel/bpf/arraymap.c
View File

@ -645,7 +645,7 @@ static const struct bpf_iter_seq_info iter_seq_info = {
.seq_priv_size = sizeof(struct bpf_iter_seq_array_map_info),
};
static int bpf_for_each_array_elem(struct bpf_map *map, void *callback_fn,
static int bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_fn,
void *callback_ctx, u64 flags)
{
u32 i, key, num_elems = 0;
@ -668,9 +668,8 @@ static int bpf_for_each_array_elem(struct bpf_map *map, void *callback_fn,
val = array->value + array->elem_size * i;
num_elems++;
key = i;
ret = BPF_CAST_CALL(callback_fn)((u64)(long)map,
(u64)(long)&key, (u64)(long)val,
(u64)(long)callback_ctx, 0);
ret = callback_fn((u64)(long)map, (u64)(long)&key,
(u64)(long)val, (u64)(long)callback_ctx, 0);
/* return value: 0 - continue, 1 - stop and return */
if (ret)
break;

13
kernel/bpf/hashtab.c
View File

@ -668,7 +668,7 @@ static int htab_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem,
(void *(*)(struct bpf_map *map, void *key))NULL));
*insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__htab_map_lookup_elem));
*insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem);
*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 1);
*insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
offsetof(struct htab_elem, key) +
@ -709,7 +709,7 @@ static int htab_lru_map_gen_lookup(struct bpf_map *map,
BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem,
(void *(*)(struct bpf_map *map, void *key))NULL));
*insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__htab_map_lookup_elem));
*insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem);
*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 4);
*insn++ = BPF_LDX_MEM(BPF_B, ref_reg, ret,
offsetof(struct htab_elem, lru_node) +
@ -2049,7 +2049,7 @@ static const struct bpf_iter_seq_info iter_seq_info = {
.seq_priv_size = sizeof(struct bpf_iter_seq_hash_map_info),
};
static int bpf_for_each_hash_elem(struct bpf_map *map, void *callback_fn,
static int bpf_for_each_hash_elem(struct bpf_map *map, bpf_callback_t callback_fn,
void *callback_ctx, u64 flags)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
@ -2089,9 +2089,8 @@ static int bpf_for_each_hash_elem(struct bpf_map *map, void *callback_fn,
val = elem->key + roundup_key_size;
}
num_elems++;
ret = BPF_CAST_CALL(callback_fn)((u64)(long)map,
(u64)(long)key, (u64)(long)val,
(u64)(long)callback_ctx, 0);
ret = callback_fn((u64)(long)map, (u64)(long)key,
(u64)(long)val, (u64)(long)callback_ctx, 0);
/* return value: 0 - continue, 1 - stop and return */
if (ret) {
rcu_read_unlock();
@ -2397,7 +2396,7 @@ static int htab_of_map_gen_lookup(struct bpf_map *map,
BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem,
(void *(*)(struct bpf_map *map, void *key))NULL));
*insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__htab_map_lookup_elem));
*insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem);
*insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 2);
*insn++ = BPF_ALU64_IMM(BPF_ADD, ret,
offsetof(struct htab_elem, key) +

5
kernel/bpf/helpers.c
View File

@ -1056,7 +1056,7 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
struct bpf_hrtimer *t = container_of(hrtimer, struct bpf_hrtimer, timer);
struct bpf_map *map = t->map;
void *value = t->value;
void *callback_fn;
bpf_callback_t callback_fn;
void *key;
u32 idx;
@ -1081,8 +1081,7 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
key = value - round_up(map->key_size, 8);
}
BPF_CAST_CALL(callback_fn)((u64)(long)map, (u64)(long)key,
(u64)(long)value, 0, 0);
callback_fn((u64)(long)map, (u64)(long)key, (u64)(long)value, 0, 0);
/* The verifier checked that return value is zero. */
this_cpu_write(hrtimer_running, NULL);

26
kernel/bpf/verifier.c
View File

@ -1744,7 +1744,7 @@ static int add_kfunc_call(struct bpf_verifier_env *env, u32 func_id)
desc = &tab->descs[tab->nr_descs++];
desc->func_id = func_id;
desc->imm = BPF_CAST_CALL(addr) - __bpf_call_base;
desc->imm = BPF_CALL_IMM(addr);
err = btf_distill_func_proto(&env->log, btf_vmlinux,
func_proto, func_name,
&desc->func_model);
@ -12514,8 +12514,7 @@ static int jit_subprogs(struct bpf_verifier_env *env)
if (!bpf_pseudo_call(insn))
continue;
subprog = insn->off;
insn->imm = BPF_CAST_CALL(func[subprog]->bpf_func) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(func[subprog]->bpf_func);
}
/* we use the aux data to keep a list of the start addresses
@ -12995,32 +12994,25 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
patch_map_ops_generic:
switch (insn->imm) {
case BPF_FUNC_map_lookup_elem:
insn->imm = BPF_CAST_CALL(ops->map_lookup_elem) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_lookup_elem);
continue;
case BPF_FUNC_map_update_elem:
insn->imm = BPF_CAST_CALL(ops->map_update_elem) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_update_elem);
continue;
case BPF_FUNC_map_delete_elem:
insn->imm = BPF_CAST_CALL(ops->map_delete_elem) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_delete_elem);
continue;
case BPF_FUNC_map_push_elem:
insn->imm = BPF_CAST_CALL(ops->map_push_elem) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_push_elem);
continue;
case BPF_FUNC_map_pop_elem:
insn->imm = BPF_CAST_CALL(ops->map_pop_elem) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_pop_elem);
continue;
case BPF_FUNC_map_peek_elem:
insn->imm = BPF_CAST_CALL(ops->map_peek_elem) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_peek_elem);
continue;
case BPF_FUNC_redirect_map:
insn->imm = BPF_CAST_CALL(ops->map_redirect) -
__bpf_call_base;
insn->imm = BPF_CALL_IMM(ops->map_redirect);
continue;
}

2
lib/test_bpf.c
View File

@ -12439,7 +12439,7 @@ static __init int prepare_tail_call_tests(struct bpf_array **pprogs)
err = -EFAULT;
goto out_err;
}
*insn = BPF_EMIT_CALL(BPF_CAST_CALL(addr));
*insn = BPF_EMIT_CALL(addr);
if ((long)__bpf_call_base + insn->imm != addr)
*insn = BPF_JMP_A(0); /* Skip: NOP */
break;