bpf: implement getsockopt and setsockopt hooks
Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and
BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks.
BPF_CGROUP_SETSOCKOPT can modify user setsockopt arguments before
passing them down to the kernel or bypass kernel completely.
BPF_CGROUP_GETSOCKOPT can can inspect/modify getsockopt arguments that
kernel returns.
Both hooks reuse existing PTR_TO_PACKET{,_END} infrastructure.
The buffer memory is pre-allocated (because I don't think there is
a precedent for working with __user memory from bpf). This might be
slow to do for each {s,g}etsockopt call, that's why I've added
__cgroup_bpf_prog_array_is_empty that exits early if there is nothing
attached to a cgroup. Note, however, that there is a race between
__cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup
program layout might have changed; this should not be a problem
because in general there is a race between multiple calls to
{s,g}etsocktop and user adding/removing bpf progs from a cgroup.
The return code of the BPF program is handled as follows:
* 0: EPERM
* 1: success, continue with next BPF program in the cgroup chain
v9:
* allow overwriting setsockopt arguments (Alexei Starovoitov):
* use set_fs (same as kernel_setsockopt)
* buffer is always kzalloc'd (no small on-stack buffer)
v8:
* use s32 for optlen (Andrii Nakryiko)
v7:
* return only 0 or 1 (Alexei Starovoitov)
* always run all progs (Alexei Starovoitov)
* use optval=0 as kernel bypass in setsockopt (Alexei Starovoitov)
(decided to use optval=-1 instead, optval=0 might be a valid input)
* call getsockopt hook after kernel handlers (Alexei Starovoitov)
v6:
* rework cgroup chaining; stop as soon as bpf program returns
0 or 2; see patch with the documentation for the details
* drop Andrii's and Martin's Acked-by (not sure they are comfortable
with the new state of things)
v5:
* skip copy_to_user() and put_user() when ret == 0 (Martin Lau)
v4:
* don't export bpf_sk_fullsock helper (Martin Lau)
* size != sizeof(__u64) for uapi pointers (Martin Lau)
* offsetof instead of bpf_ctx_range when checking ctx access (Martin Lau)
v3:
* typos in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY comments (Andrii Nakryiko)
* reverse christmas tree in BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY (Andrii
Nakryiko)
* use __bpf_md_ptr instead of __u32 for optval{,_end} (Martin Lau)
* use BPF_FIELD_SIZEOF() for consistency (Martin Lau)
* new CG_SOCKOPT_ACCESS macro to wrap repeated parts
v2:
* moved bpf_sockopt_kern fields around to remove a hole (Martin Lau)
* aligned bpf_sockopt_kern->buf to 8 bytes (Martin Lau)
* bpf_prog_array_is_empty instead of bpf_prog_array_length (Martin Lau)
* added [0,2] return code check to verifier (Martin Lau)
* dropped unused buf[64] from the stack (Martin Lau)
* use PTR_TO_SOCKET for bpf_sockopt->sk (Martin Lau)
* dropped bpf_target_off from ctx rewrites (Martin Lau)
* use return code for kernel bypass (Martin Lau & Andrii Nakryiko)
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Martin Lau <kafai@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7713cf3..b0f545e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1590,6 +1590,14 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type,
default:
return -EINVAL;
}
+ case BPF_PROG_TYPE_CGROUP_SOCKOPT:
+ switch (expected_attach_type) {
+ case BPF_CGROUP_SETSOCKOPT:
+ case BPF_CGROUP_GETSOCKOPT:
+ return 0;
+ default:
+ return -EINVAL;
+ }
default:
return 0;
}
@@ -1840,6 +1848,7 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
switch (prog->type) {
case BPF_PROG_TYPE_CGROUP_SOCK:
case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
+ case BPF_PROG_TYPE_CGROUP_SOCKOPT:
return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
case BPF_PROG_TYPE_CGROUP_SKB:
return prog->enforce_expected_attach_type &&
@@ -1912,6 +1921,10 @@ static int bpf_prog_attach(const union bpf_attr *attr)
case BPF_CGROUP_SYSCTL:
ptype = BPF_PROG_TYPE_CGROUP_SYSCTL;
break;
+ case BPF_CGROUP_GETSOCKOPT:
+ case BPF_CGROUP_SETSOCKOPT:
+ ptype = BPF_PROG_TYPE_CGROUP_SOCKOPT;
+ break;
default:
return -EINVAL;
}
@@ -1995,6 +2008,10 @@ static int bpf_prog_detach(const union bpf_attr *attr)
case BPF_CGROUP_SYSCTL:
ptype = BPF_PROG_TYPE_CGROUP_SYSCTL;
break;
+ case BPF_CGROUP_GETSOCKOPT:
+ case BPF_CGROUP_SETSOCKOPT:
+ ptype = BPF_PROG_TYPE_CGROUP_SOCKOPT;
+ break;
default:
return -EINVAL;
}
@@ -2031,6 +2048,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
case BPF_CGROUP_SOCK_OPS:
case BPF_CGROUP_DEVICE:
case BPF_CGROUP_SYSCTL:
+ case BPF_CGROUP_GETSOCKOPT:
+ case BPF_CGROUP_SETSOCKOPT:
break;
case BPF_LIRC_MODE2:
return lirc_prog_query(attr, uattr);