Within BPF syscall handling code CAP_NET_ADMIN checks stand out a bit
compared to CAP_BPF and CAP_PERFMON checks. For the latter, CAP_BPF or
CAP_PERFMON are checked first, but if they are not set, CAP_SYS_ADMIN
takes over and grants whatever part of BPF syscall is required.
Similar kind of checks that involve CAP_NET_ADMIN are not so consistent.
One out of four uses does follow CAP_BPF/CAP_PERFMON model: during
BPF_PROG_LOAD, if the type of BPF program is "network-related" either
CAP_NET_ADMIN or CAP_SYS_ADMIN is required to proceed.
But in three other cases CAP_NET_ADMIN is required even if CAP_SYS_ADMIN
is set:
- when creating DEVMAP/XDKMAP/CPU_MAP maps;
- when attaching CGROUP_SKB programs;
- when handling BPF_PROG_QUERY command.
This patch is changing the latter three cases to follow BPF_PROG_LOAD
model, that is allowing to proceed under either CAP_NET_ADMIN or
CAP_SYS_ADMIN.
This also makes it cleaner in subsequent BPF token patches to switch
wholesomely to a generic bpf_token_capable(int cap) check, that always
falls back to CAP_SYS_ADMIN if requested capability is missing.
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
kernel/bpf/syscall.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6b5280f14a53..7445dad01fb3 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1097,6 +1097,11 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
return ret;
}
+static bool bpf_net_capable(void)
+{
+ return capable(CAP_NET_ADMIN) || capable(CAP_SYS_ADMIN);
+}
+
#define BPF_MAP_CREATE_LAST_FIELD map_extra
/* called via syscall */
static int map_create(union bpf_attr *attr)
@@ -1200,7 +1205,7 @@ static int map_create(union bpf_attr *attr)
case BPF_MAP_TYPE_DEVMAP:
case BPF_MAP_TYPE_DEVMAP_HASH:
case BPF_MAP_TYPE_XSKMAP:
- if (!capable(CAP_NET_ADMIN))
+ if (!bpf_net_capable())
return -EPERM;
break;
default:
@@ -2595,7 +2600,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
!bpf_capable())
return -EPERM;
- if (is_net_admin_prog_type(type) && !capable(CAP_NET_ADMIN) && !capable(CAP_SYS_ADMIN))
+ if (is_net_admin_prog_type(type) && !bpf_net_capable())
return -EPERM;
if (is_perfmon_prog_type(type) && !perfmon_capable())
return -EPERM;
@@ -3740,7 +3745,7 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
case BPF_PROG_TYPE_SK_LOOKUP:
return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
case BPF_PROG_TYPE_CGROUP_SKB:
- if (!capable(CAP_NET_ADMIN))
+ if (!bpf_net_capable())
/* cg-skb progs can be loaded by unpriv user.
* check permissions at attach time.
*/
@@ -3924,7 +3929,7 @@ static int bpf_prog_detach(const union bpf_attr *attr)
static int bpf_prog_query(const union bpf_attr *attr,
union bpf_attr __user *uattr)
{
- if (!capable(CAP_NET_ADMIN))
+ if (!bpf_net_capable())
return -EPERM;
if (CHECK_ATTR(BPF_PROG_QUERY))
return -EINVAL;
--
2.34.1
