[PATCH bpf-next] bpf: skip unnecessary capability check

[Chenbo Feng]

From: Chenbo Feng <fe...@google.com>

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 <fe...@google.com>
---
 kernel/bpf/syscall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e24aa3241387..43f95d190eea 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1845,7 +1845,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, 
uattr, unsigned int, siz
        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);
-- 
2.16.2.804.g6dcf76e118-goog