diff options
author | Stanislav Fomichev <sdf@google.com> | 2019-06-27 13:38:47 -0700 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2019-06-27 15:25:16 -0700 |
commit | 0d01da6afc5402f60325c5da31b22f7d56689b49 (patch) | |
tree | afb8dd2975f8aa50d3577cb42310eb298d6491ac /net | |
parent | 3b1c667e47e4066cfe61610825ad50bc6b4a57e1 (diff) | |
download | linux-0d01da6afc5402f60325c5da31b22f7d56689b49.tar.bz2 |
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>
Diffstat (limited to 'net')
-rw-r--r-- | net/core/filter.c | 2 | ||||
-rw-r--r-- | net/socket.c | 30 |
2 files changed, 31 insertions, 1 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index 2014d76e0d2a..dc8534be12fc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5651,7 +5651,7 @@ BPF_CALL_1(bpf_tcp_sock, struct sock *, sk) return (unsigned long)NULL; } -static const struct bpf_func_proto bpf_tcp_sock_proto = { +const struct bpf_func_proto bpf_tcp_sock_proto = { .func = bpf_tcp_sock, .gpl_only = false, .ret_type = RET_PTR_TO_TCP_SOCK_OR_NULL, diff --git a/net/socket.c b/net/socket.c index 963df5dbdd54..0ddfbfb761d9 100644 --- a/net/socket.c +++ b/net/socket.c @@ -2051,6 +2051,8 @@ SYSCALL_DEFINE4(recv, int, fd, void __user *, ubuf, size_t, size, static int __sys_setsockopt(int fd, int level, int optname, char __user *optval, int optlen) { + mm_segment_t oldfs = get_fs(); + char *kernel_optval = NULL; int err, fput_needed; struct socket *sock; @@ -2063,6 +2065,22 @@ static int __sys_setsockopt(int fd, int level, int optname, if (err) goto out_put; + err = BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock->sk, &level, + &optname, optval, &optlen, + &kernel_optval); + + if (err < 0) { + goto out_put; + } else if (err > 0) { + err = 0; + goto out_put; + } + + if (kernel_optval) { + set_fs(KERNEL_DS); + optval = (char __user __force *)kernel_optval; + } + if (level == SOL_SOCKET) err = sock_setsockopt(sock, level, optname, optval, @@ -2071,6 +2089,11 @@ static int __sys_setsockopt(int fd, int level, int optname, err = sock->ops->setsockopt(sock, level, optname, optval, optlen); + + if (kernel_optval) { + set_fs(oldfs); + kfree(kernel_optval); + } out_put: fput_light(sock->file, fput_needed); } @@ -2093,6 +2116,7 @@ static int __sys_getsockopt(int fd, int level, int optname, { int err, fput_needed; struct socket *sock; + int max_optlen; sock = sockfd_lookup_light(fd, &err, &fput_needed); if (sock != NULL) { @@ -2100,6 +2124,8 @@ static int __sys_getsockopt(int fd, int level, int optname, if (err) goto out_put; + max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen); + if (level == SOL_SOCKET) err = sock_getsockopt(sock, level, optname, optval, @@ -2108,6 +2134,10 @@ static int __sys_getsockopt(int fd, int level, int optname, err = sock->ops->getsockopt(sock, level, optname, optval, optlen); + + err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname, + optval, optlen, + max_optlen, err); out_put: fput_light(sock->file, fput_needed); } |