xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

bpf: Implement bpf_prog replacement for an active bpf_cgroup_link

Browse Source 
Add new operation (LINK_UPDATE), which allows to replace active bpf_prog from
under given bpf_link. Currently this is only supported for bpf_cgroup_link,
but will be extended to other kinds of bpf_links in follow-up patches.

For bpf_cgroup_link, implemented functionality matches existing semantics for
direct bpf_prog attachment (including BPF_F_REPLACE flag). User can either
unconditionally set new bpf_prog regardless of which bpf_prog is currently
active under given bpf_link, or, optionally, can specify expected active
bpf_prog. If active bpf_prog doesn't match expected one, no changes are
performed, old bpf_link stays intact and attached, operation returns
a failure.

cgroup_bpf_replace() operation is resolving race between auto-detachment and
bpf_prog update in the same fashion as it's done for bpf_link detachment,
except in this case update has no way of succeeding because of target cgroup
marked as dying. So in this case error is returned.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200330030001.2312810-3-andriin@fb.com
This commit is contained in:
Andrii Nakryiko
2020-03-29 19:59:59 -07:00
committed by Alexei Starovoitov
parent af6eea5743
commit 0c991ebc8c
5 changed files with 186 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
kernel/bpf/syscall.c
View File

@@ -3596,6 +3596,58 @@ err_out:
return ret;
}
#define BPF_LINK_UPDATE_LAST_FIELD link_update.old_prog_fd
static int link_update(union bpf_attr *attr)
{
struct bpf_prog *old_prog = NULL, *new_prog;
struct bpf_link *link;
u32 flags;
int ret;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
if (CHECK_ATTR(BPF_LINK_UPDATE))
return -EINVAL;
flags = attr->link_update.flags;
if (flags & ~BPF_F_REPLACE)
return -EINVAL;
link = bpf_link_get_from_fd(attr->link_update.link_fd);
if (IS_ERR(link))
return PTR_ERR(link);
new_prog = bpf_prog_get(attr->link_update.new_prog_fd);
if (IS_ERR(new_prog))
return PTR_ERR(new_prog);
if (flags & BPF_F_REPLACE) {
old_prog = bpf_prog_get(attr->link_update.old_prog_fd);
if (IS_ERR(old_prog)) {
ret = PTR_ERR(old_prog);
old_prog = NULL;
goto out_put_progs;
}
}
#ifdef CONFIG_CGROUP_BPF
if (link->ops == &bpf_cgroup_link_lops) {
ret = cgroup_bpf_replace(link, old_prog, new_prog);
goto out_put_progs;
}
#endif
ret = -EINVAL;
out_put_progs:
if (old_prog)
bpf_prog_put(old_prog);
if (ret)
bpf_prog_put(new_prog);
return ret;
}
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
union bpf_attr attr = {};
@@ -3709,6 +3761,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_LINK_CREATE:
err = link_create(&attr);
break;
case BPF_LINK_UPDATE:
err = link_update(&attr);
break;
default:
err = -EINVAL;
break;