UPSTREAM: bpf: Add support for forced LINK_DETACH command

Add LINK_DETACH command to force-detach bpf_link without destroying it. It has
the same behavior as auto-detaching of bpf_link due to cgroup dying for
bpf_cgroup_link or net_device being destroyed for bpf_xdp_link. In such case,
bpf_link is still a valid kernel object, but is defuncts and doesn't hold BPF
program attached to corresponding BPF hook. This functionality allows users
with enough access rights to manually force-detach attached bpf_link without
killing respective owner process.

This patch implements LINK_DETACH for cgroup, xdp, and netns links, mostly
re-using existing link release handling code.

Change-Id: If3c5405705d29eeb6be32bbbf662d4e36d28c3e3
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200731182830.286260-2-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-07-31 11:28:26 -07:00 • committed by basamaryan
commit dd737ca5f3
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GPG key ID: 210D5384FB2A5885
6 changed files with 64 additions and 2 deletions

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@ -117,6 +117,7 @@ enum bpf_cmd {
BPF_LINK_GET_NEXT_ID,
BPF_ENABLE_STATS,
BPF_ITER_CREATE,
BPF_LINK_DETACH,
};
enum bpf_map_type {
@ -634,6 +635,10 @@ union bpf_attr {
__u32 old_prog_fd;
} link_update;
struct {
__u32 link_fd;
} link_detach;
struct { /* struct used by BPF_ENABLE_STATS command */
__u32 type;
} enable_stats;