Allows cgroup inet skb programs to return values in the range [0, 3].
The second bit is used to deterine if congestion occurred and higher
level protocol should decrease rate. E.g. TCP would call tcp_enter_cwr()
The bpf_prog must set expected_attach_type to BPF_CGROUP_INET_EGRESS
at load time if it uses the new return values (i.e. 2 or 3).
The expected_attach_type is currently not enforced for
BPF_PROG_TYPE_CGROUP_SKB. e.g Meaning the current bpf_prog with
expected_attach_type setting to BPF_CGROUP_INET_EGRESS can attach to
BPF_CGROUP_INET_INGRESS. Blindly enforcing expected_attach_type will
break backward compatibility.
This patch adds a enforce_expected_attach_type bit to only
enforce the expected_attach_type when it uses the new
return value.
Signed-off-by: Lawrence Brakmo <bra...@fb.com>
Signed-off-by: Martin KaFai Lau <ka...@fb.com>
---
include/linux/filter.h | 3 ++-
kernel/bpf/syscall.c | 12 ++++++++++++
kernel/bpf/verifier.c | 16 +++++++++++++---
3 files changed, 27 insertions(+), 4 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index ba8b65270e0d..43b45d6db36d 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -526,7 +526,8 @@ struct bpf_prog {
blinded:1, /* Was blinded */
is_func:1, /* program is a bpf function */
kprobe_override:1, /* Do we override a kprobe?
*/
- has_callchain_buf:1; /* callchain buffer
allocated? */
+ has_callchain_buf:1, /* callchain buffer
allocated? */
+ enforce_expected_attach_type:1; /* Enforce
expected_attach_type checking at attach time */
enum bpf_prog_type type; /* Type of BPF program */
enum bpf_attach_type expected_attach_type; /* For some prog types */
u32 len; /* Number of filter blocks */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 3d546b6f4646..1539774d78c7 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1585,6 +1585,14 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type
prog_type,
default:
return -EINVAL;
}
+ case BPF_PROG_TYPE_CGROUP_SKB:
+ switch (expected_attach_type) {
+ case BPF_CGROUP_INET_INGRESS:
+ case BPF_CGROUP_INET_EGRESS:
+ return 0;
+ default:
+ return -EINVAL;
+ }
default:
return 0;
}
@@ -1836,6 +1844,10 @@ static int bpf_prog_attach_check_attach_type(const
struct bpf_prog *prog,
case BPF_PROG_TYPE_CGROUP_SOCK:
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
+ case BPF_PROG_TYPE_CGROUP_SKB:
+ return prog->enforce_expected_attach_type &&
+ prog->expected_attach_type != attach_type ?
+ -EINVAL : 0;
default:
return 0;
}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2778417e6e0c..5c2cb5bd84ce 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5508,11 +5508,16 @@ static int check_ld_abs(struct bpf_verifier_env *env,
struct bpf_insn *insn)
static int check_return_code(struct bpf_verifier_env *env)
{
+ struct tnum enforce_attach_type_range = tnum_unknown;
struct bpf_reg_state *reg;
struct tnum range = tnum_range(0, 1);
switch (env->prog->type) {
case BPF_PROG_TYPE_CGROUP_SKB:
+ if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
+ range = tnum_range(0, 3);
+ enforce_attach_type_range = tnum_range(2, 3);
+ }
case BPF_PROG_TYPE_CGROUP_SOCK:
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
case BPF_PROG_TYPE_SOCK_OPS:
@@ -5531,18 +5536,23 @@ static int check_return_code(struct bpf_verifier_env
*env)
}
if (!tnum_in(range, reg->var_off)) {
+ char tn_buf[48];
+
verbose(env, "At program exit the register R0 ");
if (!tnum_is_unknown(reg->var_off)) {
- char tn_buf[48];
-
tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
verbose(env, "has value %s", tn_buf);
} else {
verbose(env, "has unknown scalar value");
}
- verbose(env, " should have been 0 or 1\n");
+ tnum_strn(tn_buf, sizeof(tn_buf), range);
+ verbose(env, " should have been %s\n", tn_buf);
return -EINVAL;
}
+
+ if (!tnum_is_unknown(enforce_attach_type_range) &&
+ tnum_in(enforce_attach_type_range, reg->var_off))
+ env->prog->enforce_expected_attach_type = 1;
return 0;
}
--
2.17.1
