diff options
author | Andrii Nakryiko <andriin@fb.com> | 2020-07-31 11:28:26 -0700 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2020-08-01 20:38:28 -0700 |
commit | 73b11c2ab072d5b0599d1e12cc126f55ee306daf (patch) | |
tree | 0b005d7d70f073d7d908e0d2a1fb263405f3971b /kernel | |
parent | 4939b2847d26c025e2e2118744226967f239a1ac (diff) |
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 <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
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/bpf/cgroup.c | 15 | ||||
-rw-r--r-- | kernel/bpf/net_namespace.c | 8 | ||||
-rw-r--r-- | kernel/bpf/syscall.c | 26 |
3 files changed, 48 insertions, 1 deletions
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, diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c index 71405edd667c..542f275bf252 100644 --- a/kernel/bpf/net_namespace.c +++ b/kernel/bpf/net_namespace.c @@ -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, diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index cd3d599e9e90..2f343ce15747 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3991,6 +3991,29 @@ out_put_link: return ret; } +#define BPF_LINK_DETACH_LAST_FIELD link_detach.link_fd + +static int link_detach(union bpf_attr *attr) +{ + struct bpf_link *link; + int ret; + + if (CHECK_ATTR(BPF_LINK_DETACH)) + return -EINVAL; + + link = bpf_link_get_from_fd(attr->link_detach.link_fd); + if (IS_ERR(link)) + return PTR_ERR(link); + + if (link->ops->detach) + ret = link->ops->detach(link); + else + ret = -EOPNOTSUPP; + + bpf_link_put(link); + return ret; +} + static int bpf_link_inc_not_zero(struct bpf_link *link) { return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? 0 : -ENOENT; @@ -4240,6 +4263,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz case BPF_ITER_CREATE: err = bpf_iter_create(&attr); break; + case BPF_LINK_DETACH: + err = link_detach(&attr); + break; default: err = -EINVAL; break; |