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authorAlexei Starovoitov <ast@plumgrid.com>2015-06-04 10:11:54 -0700
committerDavid S. Miller <davem@davemloft.net>2015-06-07 02:01:33 -0700
commitd691f9e8d4405c334aa10d556e73c8bf44cb0e01 (patch)
tree295b1d647364407c42990d916358a72381f4d534 /kernel/bpf
parent3431205e03977aaf32bce6d4b16fb8244b510056 (diff)
bpf: allow programs to write to certain skb fields
allow programs read/write skb->mark, tc_index fields and ((struct qdisc_skb_cb *)cb)->data. mark and tc_index are generically useful in TC. cb[0]-cb[4] are primarily used to pass arguments from one program to another called via bpf_tail_call() which can be seen in sockex3_kern.c example. All fields of 'struct __sk_buff' are readable to socket and tc_cls_act progs. mark, tc_index are writeable from tc_cls_act only. cb[0]-cb[4] are writeable by both sockets and tc_cls_act. Add verifier tests and improve sample code. Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c37
1 files changed, 28 insertions, 9 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cfd9a40b9a5a..039d866fd36a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1692,6 +1692,8 @@ static int do_check(struct verifier_env *env)
}
} else if (class == BPF_STX) {
+ enum bpf_reg_type dst_reg_type;
+
if (BPF_MODE(insn->code) == BPF_XADD) {
err = check_xadd(env, insn);
if (err)
@@ -1700,11 +1702,6 @@ static int do_check(struct verifier_env *env)
continue;
}
- if (BPF_MODE(insn->code) != BPF_MEM ||
- insn->imm != 0) {
- verbose("BPF_STX uses reserved fields\n");
- return -EINVAL;
- }
/* check src1 operand */
err = check_reg_arg(regs, insn->src_reg, SRC_OP);
if (err)
@@ -1714,6 +1711,8 @@ static int do_check(struct verifier_env *env)
if (err)
return err;
+ dst_reg_type = regs[insn->dst_reg].type;
+
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_WRITE,
@@ -1721,6 +1720,15 @@ 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 &&
+ (dst_reg_type == PTR_TO_CTX ||
+ insn->imm == PTR_TO_CTX)) {
+ verbose("same insn cannot be used with different pointers\n");
+ return -EINVAL;
+ }
+
} else if (class == BPF_ST) {
if (BPF_MODE(insn->code) != BPF_MEM ||
insn->src_reg != BPF_REG_0) {
@@ -1839,12 +1847,18 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
for (i = 0; i < insn_cnt; i++, insn++) {
if (BPF_CLASS(insn->code) == BPF_LDX &&
- (BPF_MODE(insn->code) != BPF_MEM ||
- insn->imm != 0)) {
+ (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
verbose("BPF_LDX uses reserved fields\n");
return -EINVAL;
}
+ if (BPF_CLASS(insn->code) == BPF_STX &&
+ ((BPF_MODE(insn->code) != BPF_MEM &&
+ BPF_MODE(insn->code) != BPF_XADD) || insn->imm != 0)) {
+ verbose("BPF_STX uses reserved fields\n");
+ return -EINVAL;
+ }
+
if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
struct bpf_map *map;
struct fd f;
@@ -1967,12 +1981,17 @@ static int convert_ctx_accesses(struct verifier_env *env)
struct bpf_prog *new_prog;
u32 cnt;
int i;
+ enum bpf_access_type type;
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))
+ if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
+ type = BPF_READ;
+ else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
+ type = BPF_WRITE;
+ else
continue;
if (insn->imm != PTR_TO_CTX) {
@@ -1982,7 +2001,7 @@ static int convert_ctx_accesses(struct verifier_env *env)
}
cnt = env->prog->aux->ops->
- convert_ctx_access(insn->dst_reg, insn->src_reg,
+ convert_ctx_access(type, insn->dst_reg, insn->src_reg,
insn->off, insn_buf);
if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
verbose("bpf verifier is misconfigured\n");