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bpf: flow_dissector: Check value of unused flags to BPF_PROG_DETACH

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Using BPF_PROG_DETACH on a flow dissector program supports neither
attach_flags nor attach_bpf_fd. Yet no value is enforced for them.

Enforce that attach_flags are zero, and require the current program
to be passed via attach_bpf_fd. This allows us to remove the check
for CAP_SYS_ADMIN, since userspace can now no longer remove
arbitrary flow dissector programs.

Fixes: b27f7bb590 ("flow_dissector: Move out netns_bpf prog callbacks")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200629095630.7933-3-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer
2020-06-29 10:56:26 +01:00
committed by Alexei Starovoitov
parent 1b514239e8
commit 4ac2add659
3 changed files with 19 additions and 9 deletions
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19
kernel/bpf/net_namespace.c
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@@ -269,7 +269,8 @@ out_unlock:
/* Must be called with netns_bpf_mutex held. */
static int __netns_bpf_prog_detach(struct net *net,
enum netns_bpf_attach_type type)
enum netns_bpf_attach_type type,
struct bpf_prog *old)
{
struct bpf_prog *attached;
@@ -278,7 +279,7 @@ static int __netns_bpf_prog_detach(struct net *net,
return -EINVAL;
attached = net->bpf.progs[type];
if (!attached)
if (!attached || attached != old)
return -ENOENT;
netns_bpf_run_array_detach(net, type);
net->bpf.progs[type] = NULL;
@@ -286,19 +287,29 @@ static int __netns_bpf_prog_detach(struct net *net,
return 0;
}
int netns_bpf_prog_detach(const union bpf_attr *attr)
int netns_bpf_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
{
enum netns_bpf_attach_type type;
struct bpf_prog *prog;
int ret;
if (attr->target_fd)
return -EINVAL;
type = to_netns_bpf_attach_type(attr->attach_type);
if (type < 0)
return -EINVAL;
prog = bpf_prog_get_type(attr->attach_bpf_fd, ptype);
if (IS_ERR(prog))
return PTR_ERR(prog);
mutex_lock(&netns_bpf_mutex);
ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type);
ret = __netns_bpf_prog_detach(current->nsproxy->net_ns, type, prog);
mutex_unlock(&netns_bpf_mutex);
bpf_prog_put(prog);
return ret;
}