From 73b11c2ab072d5b0599d1e12cc126f55ee306daf Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 31 Jul 2020 11:28:26 -0700 Subject: 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. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov Acked-by: Song Liu Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/20200731182830.286260-2-andriin@fb.com --- kernel/bpf/cgroup.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'kernel/bpf/cgroup.c') diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 957cce1d5168..83ff127ef7ae 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -814,6 +814,7 @@ static void bpf_cgroup_link_release(struct bpf_link *link) { struct bpf_cgroup_link *cg_link = container_of(link, struct bpf_cgroup_link, link); + struct cgroup *cg; /* link might have been auto-detached by dying cgroup already, * in that case our work is done here @@ -832,8 +833,12 @@ static void bpf_cgroup_link_release(struct bpf_link *link) WARN_ON(__cgroup_bpf_detach(cg_link->cgroup, NULL, cg_link, cg_link->type)); + cg = cg_link->cgroup; + cg_link->cgroup = NULL; + mutex_unlock(&cgroup_mutex); - cgroup_put(cg_link->cgroup); + + cgroup_put(cg); } static void bpf_cgroup_link_dealloc(struct bpf_link *link) @@ -844,6 +849,13 @@ static void bpf_cgroup_link_dealloc(struct bpf_link *link) kfree(cg_link); } +static int bpf_cgroup_link_detach(struct bpf_link *link) +{ + bpf_cgroup_link_release(link); + + return 0; +} + static void bpf_cgroup_link_show_fdinfo(const struct bpf_link *link, struct seq_file *seq) { @@ -883,6 +895,7 @@ static int bpf_cgroup_link_fill_link_info(const struct bpf_link *link, static const struct bpf_link_ops bpf_cgroup_link_lops = { .release = bpf_cgroup_link_release, .dealloc = bpf_cgroup_link_dealloc, + .detach = bpf_cgroup_link_detach, .update_prog = cgroup_bpf_replace, .show_fdinfo = bpf_cgroup_link_show_fdinfo, .fill_link_info = bpf_cgroup_link_fill_link_info, -- cgit v1.2.3-71-gd317