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Date: Wed, 21 Sep 2016 11:43:56 +0100
From: Jakub Kicinski <jakub.kicinski@...ronome.com>
To: netdev@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net,
Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCHv7 net-next 04/15] bpf: don't (ab)use instructions to store state
Storing state in reserved fields of instructions makes
it impossible to run verifier on programs already
marked as read-only. Allocate and use an array of
per-instruction state instead.
While touching the error path rename and move existing
jump target.
Suggested-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
---
v7:
- fix insn offsets when patching is happening in
convert_ctx_accesses().
v3:
- new patch.
---
kernel/bpf/verifier.c | 70 +++++++++++++++++++++++++++++----------------------
1 file changed, 40 insertions(+), 30 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3a75ee3bdcd1..a9542d89f293 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -181,6 +181,10 @@ struct verifier_stack_elem {
struct verifier_stack_elem *next;
};
+struct bpf_insn_aux_data {
+ enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
+};
+
#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
/* single container for all structs
@@ -197,6 +201,7 @@ struct verifier_env {
u32 id_gen; /* used to generate unique reg IDs */
bool allow_ptr_leaks;
bool seen_direct_write;
+ struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
};
#define BPF_COMPLEXITY_LIMIT_INSNS 65536
@@ -2344,7 +2349,7 @@ static int do_check(struct verifier_env *env)
return err;
} else if (class == BPF_LDX) {
- enum bpf_reg_type src_reg_type;
+ enum bpf_reg_type *prev_src_type, src_reg_type;
/* check for reserved fields is already done */
@@ -2374,16 +2379,18 @@ static int do_check(struct verifier_env *env)
continue;
}
- if (insn->imm == 0) {
+ prev_src_type = &env->insn_aux_data[insn_idx].ptr_type;
+
+ if (*prev_src_type == NOT_INIT) {
/* saw a valid insn
* dst_reg = *(u32 *)(src_reg + off)
- * use reserved 'imm' field to mark this insn
+ * save type to validate intersecting paths
*/
- insn->imm = src_reg_type;
+ *prev_src_type = src_reg_type;
- } else if (src_reg_type != insn->imm &&
+ } else if (src_reg_type != *prev_src_type &&
(src_reg_type == PTR_TO_CTX ||
- insn->imm == PTR_TO_CTX)) {
+ *prev_src_type == PTR_TO_CTX)) {
/* ABuser program is trying to use the same insn
* dst_reg = *(u32*) (src_reg + off)
* with different pointer types:
@@ -2396,7 +2403,7 @@ static int do_check(struct verifier_env *env)
}
} else if (class == BPF_STX) {
- enum bpf_reg_type dst_reg_type;
+ enum bpf_reg_type *prev_dst_type, dst_reg_type;
if (BPF_MODE(insn->code) == BPF_XADD) {
err = check_xadd(env, insn);
@@ -2424,11 +2431,13 @@ static int do_check(struct verifier_env *env)
if (err)
return err;
- if (insn->imm == 0) {
- insn->imm = dst_reg_type;
- } else if (dst_reg_type != insn->imm &&
+ prev_dst_type = &env->insn_aux_data[insn_idx].ptr_type;
+
+ if (*prev_dst_type == NOT_INIT) {
+ *prev_dst_type = dst_reg_type;
+ } else if (dst_reg_type != *prev_dst_type &&
(dst_reg_type == PTR_TO_CTX ||
- insn->imm == PTR_TO_CTX)) {
+ *prev_dst_type == PTR_TO_CTX)) {
verbose("same insn cannot be used with different pointers\n");
return -EINVAL;
}
@@ -2686,10 +2695,11 @@ static void convert_pseudo_ld_imm64(struct verifier_env *env)
static int convert_ctx_accesses(struct verifier_env *env)
{
const struct bpf_verifier_ops *ops = env->prog->aux->ops;
+ const int insn_cnt = env->prog->len;
struct bpf_insn insn_buf[16], *insn;
struct bpf_prog *new_prog;
enum bpf_access_type type;
- int i, insn_cnt, cnt;
+ int i, cnt, delta = 0;
if (ops->gen_prologue) {
cnt = ops->gen_prologue(insn_buf, env->seen_direct_write,
@@ -2703,18 +2713,16 @@ static int convert_ctx_accesses(struct verifier_env *env)
if (!new_prog)
return -ENOMEM;
env->prog = new_prog;
+ delta += cnt - 1;
}
}
if (!ops->convert_ctx_access)
return 0;
- insn_cnt = env->prog->len;
- insn = env->prog->insnsi;
+ insn = env->prog->insnsi + delta;
for (i = 0; i < insn_cnt; i++, insn++) {
- u32 insn_delta;
-
if (insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
type = BPF_READ;
@@ -2724,11 +2732,8 @@ static int convert_ctx_accesses(struct verifier_env *env)
else
continue;
- if (insn->imm != PTR_TO_CTX) {
- /* clear internal mark */
- insn->imm = 0;
+ if (env->insn_aux_data[i].ptr_type != PTR_TO_CTX)
continue;
- }
cnt = ops->convert_ctx_access(type, insn->dst_reg, insn->src_reg,
insn->off, insn_buf, env->prog);
@@ -2737,18 +2742,16 @@ static int convert_ctx_accesses(struct verifier_env *env)
return -EINVAL;
}
- new_prog = bpf_patch_insn_single(env->prog, i, insn_buf, cnt);
+ new_prog = bpf_patch_insn_single(env->prog, i + delta, insn_buf,
+ cnt);
if (!new_prog)
return -ENOMEM;
- insn_delta = cnt - 1;
+ delta += cnt - 1;
/* keep walking new program and skip insns we just inserted */
env->prog = new_prog;
- insn = new_prog->insnsi + i + insn_delta;
-
- insn_cnt += insn_delta;
- i += insn_delta;
+ insn = new_prog->insnsi + i + delta;
}
return 0;
@@ -2792,6 +2795,11 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
if (!env)
return -ENOMEM;
+ env->insn_aux_data = vzalloc(sizeof(struct bpf_insn_aux_data) *
+ (*prog)->len);
+ ret = -ENOMEM;
+ if (!env->insn_aux_data)
+ goto err_free_env;
env->prog = *prog;
/* grab the mutex to protect few globals used by verifier */
@@ -2810,12 +2818,12 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
/* log_* values have to be sane */
if (log_size < 128 || log_size > UINT_MAX >> 8 ||
log_level == 0 || log_ubuf == NULL)
- goto free_env;
+ goto err_unlock;
ret = -ENOMEM;
log_buf = vmalloc(log_size);
if (!log_buf)
- goto free_env;
+ goto err_unlock;
} else {
log_level = 0;
}
@@ -2884,14 +2892,16 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
free_log_buf:
if (log_level)
vfree(log_buf);
-free_env:
if (!env->prog->aux->used_maps)
/* if we didn't copy map pointers into bpf_prog_info, release
* them now. Otherwise free_bpf_prog_info() will release them.
*/
release_maps(env);
*prog = env->prog;
- kfree(env);
+err_unlock:
mutex_unlock(&bpf_verifier_lock);
+ vfree(env->insn_aux_data);
+err_free_env:
+ kfree(env);
return ret;
}
--
1.9.1
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