From: Chenbo Feng <fengc@google.com>
Date: Mon, 19 Mar 2018 17:57:27 -0700
Subject: bpf: skip unnecessary capability check
Patch-mainline: v4.16-rc7
Git-commit: 0fa4fe85f4724fff89b09741c437cbee9cf8b008
References: bsc#1083647

The current check statement in BPF syscall will do a capability check
for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This
code path will trigger unnecessary security hooks on capability checking
and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN
access. This can be resolved by simply switch the order of the statement
and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is
allowed.

Signed-off-by: Chenbo Feng <fengc@google.com>
Acked-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Gary Lin <glin@suse.com>
---
 kernel/bpf/syscall.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1403,7 +1403,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf
 	union bpf_attr attr = {};
 	int err;
 
-	if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled)
+	if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	err = check_uarg_tail_zero(uattr, sizeof(attr), size);