Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:51178 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755200AbeCVNGL (ORCPT ); Thu, 22 Mar 2018 09:06:11 -0400 Subject: Patch "bpf/cgroup: fix a verification error for a CGROUP_DEVICE type prog" has been added to the 4.15-stable tree To: yhs@fb.com, alexander.levin@microsoft.com, daniel@iogearbox.net, gregkh@linuxfoundation.org, guro@fb.com Cc: , From: Date: Thu, 22 Mar 2018 14:06:04 +0100 Message-ID: <1521723964175133@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled bpf/cgroup: fix a verification error for a CGROUP_DEVICE type prog to the 4.15-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-cgroup-fix-a-verification-error-for-a-cgroup_device-type-prog.patch and it can be found in the queue-4.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >From foo@baz Thu Mar 22 14:03:39 CET 2018 From: Yonghong Song Date: Mon, 18 Dec 2017 10:13:44 -0800 Subject: bpf/cgroup: fix a verification error for a CGROUP_DEVICE type prog From: Yonghong Song [ Upstream commit 06ef0ccb5a36e1feba9b413ff59a04ecc4407c1c ] The tools/testing/selftests/bpf test program test_dev_cgroup fails with the following error when compiled with llvm 6.0. (I did not try with earlier versions.) libbpf: load bpf program failed: Permission denied libbpf: -- BEGIN DUMP LOG --- libbpf: 0: (61) r2 = *(u32 *)(r1 +4) 1: (b7) r0 = 0 2: (55) if r2 != 0x1 goto pc+8 R0=inv0 R1=ctx(id=0,off=0,imm=0) R2=inv1 R10=fp0 3: (69) r2 = *(u16 *)(r1 +0) invalid bpf_context access off=0 size=2 ... The culprit is the following statement in dev_cgroup.c: short type = ctx->access_type & 0xFFFF; This code is typical as the ctx->access_type is assigned as below in kernel/bpf/cgroup.c: struct bpf_cgroup_dev_ctx ctx = { .access_type = (access << 16) | dev_type, .major = major, .minor = minor, }; The compiler converts it to u16 access while the verifier cgroup_dev_is_valid_access rejects any non u32 access. This patch permits the field access_type to be accessible with type u16 and u8 as well. Signed-off-by: Yonghong Song Tested-by: Roman Gushchin Signed-off-by: Daniel Borkmann Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- include/uapi/linux/bpf.h | 3 ++- kernel/bpf/cgroup.c | 15 +++++++++++++-- 2 files changed, 15 insertions(+), 3 deletions(-) --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -995,7 +995,8 @@ struct bpf_perf_event_value { #define BPF_DEVCG_DEV_CHAR (1ULL << 1) struct bpf_cgroup_dev_ctx { - __u32 access_type; /* (access << 16) | type */ + /* access_type encoded as (BPF_DEVCG_ACC_* << 16) | BPF_DEVCG_DEV_* */ + __u32 access_type; __u32 major; __u32 minor; }; --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -568,6 +568,8 @@ static bool cgroup_dev_is_valid_access(i enum bpf_access_type type, struct bpf_insn_access_aux *info) { + const int size_default = sizeof(__u32); + if (type == BPF_WRITE) return false; @@ -576,8 +578,17 @@ static bool cgroup_dev_is_valid_access(i /* The verifier guarantees that size > 0. */ if (off % size != 0) return false; - if (size != sizeof(__u32)) - return false; + + switch (off) { + case bpf_ctx_range(struct bpf_cgroup_dev_ctx, access_type): + bpf_ctx_record_field_size(info, size_default); + if (!bpf_ctx_narrow_access_ok(off, size, size_default)) + return false; + break; + default: + if (size != size_default) + return false; + } return true; } Patches currently in stable-queue which might be from yhs@fb.com are queue-4.15/bpf-cgroup-fix-a-verification-error-for-a-cgroup_device-type-prog.patch