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bpf: Add support for forced LINK_DETACH command

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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.

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 Alexei Starovoitov
parent 4939b2847d
commit 73b11c2ab0
6 changed files with 64 additions and 2 deletions
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8
kernel/bpf/net_namespace.c
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@@ -142,9 +142,16 @@ static void bpf_netns_link_release(struct bpf_link *link)
bpf_prog_array_free(old_array);
out_unlock:
net_link->net = NULL;
mutex_unlock(&netns_bpf_mutex);
}
static int bpf_netns_link_detach(struct bpf_link *link)
{
bpf_netns_link_release(link);
return 0;
}
static void bpf_netns_link_dealloc(struct bpf_link *link)
{
struct bpf_netns_link *net_link =
@@ -228,6 +235,7 @@ static void bpf_netns_link_show_fdinfo(const struct bpf_link *link,
static const struct bpf_link_ops bpf_netns_link_ops = {
.release = bpf_netns_link_release,
.dealloc = bpf_netns_link_dealloc,
.detach = bpf_netns_link_detach,
.update_prog = bpf_netns_link_update_prog,
.fill_link_info = bpf_netns_link_fill_info,
.show_fdinfo = bpf_netns_link_show_fdinfo,