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7ae4eb14c5
Add BPF kfuncs that allow BPF LSM programs to create and use sockets for
sending data. This provides a mechanism for BPF programs to emit
telemetry. For this first patch set, it's restricted to SOCK_DGRAM
socket types with IPPROTO_UDP protocol but could be easily extended to
SOCK_STREAM and IPPROTO_TCP in the future.
The API consists of five kfuncs:
bpf_ksock_create() - Create a socket (sleepable)
bpf_ksock_connect() - Connect socket to remote address (sleepable)
bpf_ksock_send() - Send data through the socket (sleepable)
bpf_ksock_acquire() - Acquire a reference to a socket context
bpf_ksock_release() - Release a reference (cleanup via
queue_rcu_work since sock_release sleeps)
The setup kfuncs bpf_ksock_create, bpf_ksock_connect, can be called from
SYSCALL programs only. While bpf_ksock_acquire, bpf_ksock_release and
bpf_ksock_send can be called from SYSCALL and LSM programs.
The implementation follows the established kfunc lifecycle pattern
(create/acquire/release with refcounting, kptr map storage, dtor
registration). The kernel socket is wrapped in a refcounted bpf_ksock
struct. Cleanup is deferred via queue_rcu_work() because sock_release()
may sleep.
The kfuncs are only compiled when CONFIG_INET is enabled, as they
specifically support AF_INET and AF_INET6 sockets.
The socket operations go through the expected LSM hooks instead of
by-passing them like many kernel sockets since those are created by BPF
programs and thus system users. Thus, the bpf_ksock_send() kfunc, which
is exposed to LSM progs has a verifier filter protection to avoid
recursion so that the whole bpf_kfunc_set kfunc set cannot be called in
a program attached to security_socket_sendmsg(). Also, because of the
LSM checks, we prevent the use of the kfuncs from asynchronous workqueue
as the current value would then be invalid.
In bpf_ksock_create(), we copy the arg values to avoid TOCTOU races
since the kfunc can sleep and the arg values could be stored in a map
that could be re-written by BPF progs or even userspace programs if the
map is mmaped.
Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/bpf/20260813110540.103550-3-mahe.tardy@gmail.com
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| .. | ||
| preload | ||
| arena.c | ||
| arraymap.c | ||
| backtrack.c | ||
| bloom_filter.c | ||
| bpf_cgrp_storage.c | ||
| bpf_inode_storage.c | ||
| bpf_insn_array.c | ||
| bpf_iter.c | ||
| bpf_local_storage.c | ||
| bpf_lru_list.c | ||
| bpf_lru_list.h | ||
| bpf_lsm_proto.c | ||
| bpf_lsm.c | ||
| bpf_struct_ops.c | ||
| bpf_task_storage.c | ||
| btf_iter.c | ||
| btf_relocate.c | ||
| btf.c | ||
| cfg.c | ||
| cgroup_iter.c | ||
| cgroup.c | ||
| check_btf.c | ||
| cnum_defs.h | ||
| cnum.c | ||
| const_fold.c | ||
| core.c | ||
| cpumap.c | ||
| cpumask.c | ||
| crypto.c | ||
| devmap.c | ||
| diagnostics.c | ||
| diagnostics.h | ||
| disasm.c | ||
| disasm.h | ||
| dispatcher.c | ||
| dmabuf_iter.c | ||
| fixups.c | ||
| hashtab.c | ||
| helpers.c | ||
| inode.c | ||
| Kconfig | ||
| kmem_cache_iter.c | ||
| link_iter.c | ||
| liveness.c | ||
| local_storage.c | ||
| log.c | ||
| lpm_trie.c | ||
| Makefile | ||
| map_in_map.c | ||
| map_in_map.h | ||
| map_iter.c | ||
| memalloc.c | ||
| mmap_unlock_work.h | ||
| mprog.c | ||
| net_namespace.c | ||
| offload.c | ||
| percpu_freelist.c | ||
| percpu_freelist.h | ||
| prog_iter.c | ||
| queue_stack_maps.c | ||
| range_tree.c | ||
| range_tree.h | ||
| relo_core.c | ||
| reuseport_array.c | ||
| ringbuf.c | ||
| rqspinlock.c | ||
| rqspinlock.h | ||
| stackmap.c | ||
| states.c | ||
| stream.c | ||
| syscall.c | ||
| sysfs_btf.c | ||
| task_iter.c | ||
| tcx.c | ||
| tnum.c | ||
| token.c | ||
| trampoline.c | ||
| verifier.c | ||