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linux-next/kernel/bpf
Andrii Nakryiko af6eea5743 bpf: Implement bpf_link-based cgroup BPF program attachment
Implement new sub-command to attach cgroup BPF programs and return FD-based
bpf_link back on success. bpf_link, once attached to cgroup, cannot be
replaced, except by owner having its FD. Cgroup bpf_link supports only
BPF_F_ALLOW_MULTI semantics. Both link-based and prog-based BPF_F_ALLOW_MULTI
attachments can be freely intermixed.

To prevent bpf_cgroup_link from keeping cgroup alive past the point when no
BPF program can be executed, implement auto-detachment of link. When
cgroup_bpf_release() is called, all attached bpf_links are forced to release
cgroup refcounts, but they leave bpf_link otherwise active and allocated, as
well as still owning underlying bpf_prog. This is because user-space might
still have FDs open and active, so bpf_link as a user-referenced object can't
be freed yet. Once last active FD is closed, bpf_link will be freed and
underlying bpf_prog refcount will be dropped. But cgroup refcount won't be
touched, because cgroup is released already.

The inherent race between bpf_cgroup_link release (from closing last FD) and
cgroup_bpf_release() is resolved by both operations taking cgroup_mutex. So
the only additional check required is when bpf_cgroup_link attempts to detach
itself from cgroup. At that time we need to check whether there is still
cgroup associated with that link. And if not, exit with success, because
bpf_cgroup_link was already successfully detached.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Roman Gushchin <guro@fb.com>
Link: https://lore.kernel.org/bpf/20200330030001.2312810-2-andriin@fb.com
2020-03-30 17:35:59 -07:00
..
arraymap.c bpf: Add lookup and update batch ops to arraymap 2020-01-15 14:00:35 -08:00
bpf_lru_list.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
bpf_lru_list.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
bpf_lsm.c bpf: lsm: Implement attach, detach and execution 2020-03-30 01:34:00 +02:00
bpf_struct_ops_types.h bpf: tcp: Support tcp_congestion_ops in bpf 2020-01-09 08:46:18 -08:00
bpf_struct_ops.c bpf: Refactor trampoline update code 2020-03-04 13:41:05 -08:00
btf.c bpf: btf: Fix arg verification in btf_ctx_access() 2020-03-30 13:28:02 -07:00
cgroup.c bpf: Implement bpf_link-based cgroup BPF program attachment 2020-03-30 17:35:59 -07:00
core.c bpf: Enable bpf cgroup hooks to retrieve cgroup v2 and ancestor id 2020-03-27 19:40:39 -07:00
cpumap.c xdp: Make cpumap flush_list common for all map instances 2019-12-19 21:09:43 -08:00
devmap.c bpf, xdp: Remove no longer required rcu_read_{un}lock() 2020-01-27 11:16:25 +01:00
disasm.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295 2019-06-05 17:36:38 +02:00
disasm.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 295 2019-06-05 17:36:38 +02:00
dispatcher.c bpf: Remove bpf_image tree 2020-03-13 12:49:52 -07:00
hashtab.c bpf: Replace zero-length array with flexible-array member 2020-02-28 01:21:02 +01:00
helpers.c bpf: Enable bpf cgroup hooks to retrieve cgroup v2 and ancestor id 2020-03-27 19:40:39 -07:00
inode.c bpf: Introduce pinnable bpf_link abstraction 2020-03-02 22:06:27 -08:00
local_storage.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 09:54:33 -08:00
lpm_trie.c bpf: Replace zero-length array with flexible-array member 2020-02-28 01:21:02 +01:00
Makefile bpf: Introduce BPF_PROG_TYPE_LSM 2020-03-30 01:34:00 +02:00
map_in_map.c bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS 2020-01-09 08:46:18 -08:00
map_in_map.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
offload.c bpf, offload: Replace bitwise AND by logical AND in bpf_prog_offload_info_fill 2020-02-17 16:53:49 +01:00
percpu_freelist.c bpf: Dont iterate over possible CPUs with interrupts disabled 2020-02-24 16:18:20 -08:00
percpu_freelist.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
queue_stack_maps.c bpf: move memory size checks to bpf_map_charge_init() 2019-05-31 16:52:56 -07:00
reuseport_array.c net: Generate reuseport group ID on group creation 2020-02-21 22:29:45 +01:00
stackmap.c bpf/stackmap: Dont trylock mmap_sem with PREEMPT_RT and interrupts disabled 2020-02-24 16:20:10 -08:00
syscall.c bpf: Implement bpf_link-based cgroup BPF program attachment 2020-03-30 17:35:59 -07:00
sysfs_btf.c bpf: Support llvm-objcopy for vmlinux BTF 2020-03-19 12:32:38 +01:00
tnum.c bpf: Verifier, do explicit ALU32 bounds tracking 2020-03-30 14:59:53 -07:00
trampoline.c bpf: lsm: Implement attach, detach and execution 2020-03-30 01:34:00 +02:00
verifier.c bpf: Verifier, refine 32bit bound in do_refine_retval_range 2020-03-30 15:00:30 -07:00
xskmap.c xsk: Make xskmap flush_list common for all map instances 2019-12-19 21:09:43 -08:00