5 files changed, 234 insertions, 35 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 30bfd331882a..280a315de8d6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -103,6 +103,9 @@ struct bpf_verifier_ops {
          * with 'type' (read or write) is allowed
          */
         bool (*is_valid_access)(int off, int size, enum bpf_access_type type);
+
+        u32 (*convert_ctx_access)(int dst_reg, int src_reg, int ctx_off,
+                                  struct bpf_insn *insn);
 };
 
 struct bpf_prog_type_list {
@@ -133,7 +136,7 @@ struct bpf_map *bpf_map_get(struct fd f);
 void bpf_map_put(struct bpf_map *map);
 
 /* verify correctness of eBPF program */
-int bpf_check(struct bpf_prog *fp, union bpf_attr *attr);
+int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
 #else
 static inline void bpf_register_prog_type(struct bpf_prog_type_list *tl)
 {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index de1f63668daf..929545a27546 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -170,4 +170,14 @@ enum bpf_func_id {
         __BPF_FUNC_MAX_ID,
 };
 
+/* user accessible mirror of in-kernel sk_buff.
+ * new fields can only be added to the end of this structure
+ */
+struct __sk_buff {
+        __u32 len;
+        __u32 pkt_type;
+        __u32 mark;
+        __u32 queue_mapping;
+};
+
 #endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 669719ccc9ee..ea75c654af1b 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -519,7 +519,7 @@ static int bpf_prog_load(union bpf_attr *attr)
                 goto free_prog;
 
         /* run eBPF verifier */
-        err = bpf_check(prog, attr);
+        err = bpf_check(&prog, attr);
         if (err < 0)
                 goto free_used_maps;
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e6b522496250..c22ebd36fa4b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1620,11 +1620,10 @@ static int do_check(struct verifier_env *env)
                                 return err;
 
                 } else if (class == BPF_LDX) {
-                        if (BPF_MODE(insn->code) != BPF_MEM ||
-                            insn->imm != 0) {
-                                verbose("BPF_LDX uses reserved fields\n");
-                                return -EINVAL;
-                        }
+                        enum bpf_reg_type src_reg_type;
+
+                        /* check for reserved fields is already done */
+
                         /* check src operand */
                         err = check_reg_arg(regs, insn->src_reg, SRC_OP);
                         if (err)
@@ -1643,6 +1642,29 @@ static int do_check(struct verifier_env *env)
                         if (err)
                                 return err;
 
+                        src_reg_type = regs[insn->src_reg].type;
+
+                        if (insn->imm == 0 && BPF_SIZE(insn->code) == BPF_W) {
+                                /* saw a valid insn
+                                 * dst_reg = *(u32 *)(src_reg + off)
+                                 * use reserved 'imm' field to mark this insn
+                                 */
+                                insn->imm = src_reg_type;
+
+                        } else if (src_reg_type != insn->imm &&
+                                   (src_reg_type == PTR_TO_CTX ||
+                                    insn->imm == PTR_TO_CTX)) {
+                                /* ABuser program is trying to use the same insn
+                                 * dst_reg = *(u32*) (src_reg + off)
+                                 * with different pointer types:
+                                 * src_reg == ctx in one branch and
+                                 * src_reg == stack|map in some other branch.
+                                 * Reject it.
+                                 */
+                                verbose("same insn cannot be used with different pointers\n");
+                                return -EINVAL;
+                        }
+
                 } else if (class == BPF_STX) {
                         if (BPF_MODE(insn->code) == BPF_XADD) {
                                 err = check_xadd(env, insn);
@@ -1790,6 +1812,13 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
         int i, j;
 
         for (i = 0; i < insn_cnt; i++, insn++) {
+                if (BPF_CLASS(insn->code) == BPF_LDX &&
+                    (BPF_MODE(insn->code) != BPF_MEM ||
+                     insn->imm != 0)) {
+                        verbose("BPF_LDX uses reserved fields\n");
+                        return -EINVAL;
+                }
+
                 if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
                         struct bpf_map *map;
                         struct fd f;
@@ -1881,6 +1910,92 @@ static void convert_pseudo_ld_imm64(struct verifier_env *env)
                         insn->src_reg = 0;
 }
 
+static void adjust_branches(struct bpf_prog *prog, int pos, int delta)
+{
+        struct bpf_insn *insn = prog->insnsi;
+        int insn_cnt = prog->len;
+        int i;
+
+        for (i = 0; i < insn_cnt; i++, insn++) {
+                if (BPF_CLASS(insn->code) != BPF_JMP ||
+                    BPF_OP(insn->code) == BPF_CALL ||
+                    BPF_OP(insn->code) == BPF_EXIT)
+                        continue;
+
+                /* adjust offset of jmps if necessary */
+                if (i < pos && i + insn->off + 1 > pos)
+                        insn->off += delta;
+                else if (i > pos && i + insn->off + 1 < pos)
+                        insn->off -= delta;
+        }
+}
+
+/* convert load instructions that access fields of 'struct __sk_buff'
+ * into sequence of instructions that access fields of 'struct sk_buff'
+ */
+static int convert_ctx_accesses(struct verifier_env *env)
+{
+        struct bpf_insn *insn = env->prog->insnsi;
+        int insn_cnt = env->prog->len;
+        struct bpf_insn insn_buf[16];
+        struct bpf_prog *new_prog;
+        u32 cnt;
+        int i;
+
+        if (!env->prog->aux->ops->convert_ctx_access)
+                return 0;
+
+        for (i = 0; i < insn_cnt; i++, insn++) {
+                if (insn->code != (BPF_LDX | BPF_MEM | BPF_W))
+                        continue;
+
+                if (insn->imm != PTR_TO_CTX) {
+                        /* clear internal mark */
+                        insn->imm = 0;
+                        continue;
+                }
+
+                cnt = env->prog->aux->ops->
+                        convert_ctx_access(insn->dst_reg, insn->src_reg,
+                                           insn->off, insn_buf);
+                if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
+                        verbose("bpf verifier is misconfigured\n");
+                        return -EINVAL;
+                }
+
+                if (cnt == 1) {
+                        memcpy(insn, insn_buf, sizeof(*insn));
+                        continue;
+                }
+
+                /* several new insns need to be inserted. Make room for them */
+                insn_cnt += cnt - 1;
+                new_prog = bpf_prog_realloc(env->prog,
+                                            bpf_prog_size(insn_cnt),
+                                            GFP_USER);
+                if (!new_prog)
+                        return -