Patch "bpf: skip unnecessary capability check" has been added to the 4.4-stable tree

Patch "bpf: skip unnecessary capability check" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    bpf: skip unnecessary capability check

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bpf-skip-unnecessary-capability-check.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 0fa4fe85f4724fff89b09741c437cbee9cf8b008 Mon Sep 17 00:00:00 2001
From: Chenbo Feng <fengc@google.com>
Date: Mon, 19 Mar 2018 17:57:27 -0700
Subject: bpf: skip unnecessary capability check

From: Chenbo Feng <fengc@google.com>

commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/bpf/syscall.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -673,7 +673,7 @@ 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;
 
 	if (!access_ok(VERIFY_READ, uattr, 1))


Patches currently in stable-queue which might be from fengc@google.com are

queue-4.4/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch
queue-4.4/bpf-skip-unnecessary-capability-check.patch