From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755915AbcJXKVb (ORCPT ); Mon, 24 Oct 2016 06:21:31 -0400 Received: from mx2.suse.de ([195.135.220.15]:51691 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751610AbcJXKV3 (ORCPT ); Mon, 24 Oct 2016 06:21:29 -0400 From: Jiri Slaby To: tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, Jiri Slaby Subject: [PATCH] futex: make FUTEX_OP_OPARG_SHIFT unsigned Date: Mon, 24 Oct 2016 12:21:27 +0200 Message-Id: <20161024102127.28220-1-jslaby@suse.cz> X-Mailer: git-send-email 2.10.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org FUTEX_OP_OPARG_SHIFT is shifted left by 28 in futex_atomic_op_inuser and other places. Since FUTEX_OP_OPARG_SHIFT is 8, we actually do (8 << 28). But given both are ints, we perform operation with undefined behaviour about which UBSAN reports: UBSAN: Undefined behaviour in arch/x86/include/asm/futex.h:53:13 shift exponent 776 is too large for 32-bit type 'int' CPU: 1 PID: 27469 Comm: trinity-c1 Tainted: G EL 4.4.26-0-default #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.1-0-gb3ef39f-prebuilt.qemu-project.org 04/01/2014 0000000000000000 ffff880553ad7908 ffffffff81cbcc16 0000000041b58ab3 ffffffff82f515a3 ffffffff81cbcb16 ffff880553ad7930 ffff880553ad78d0 ffffffff837d7d60 0000000000000000 0000000000000308 ffffffff837d7d62 Call Trace: [] ? __ubsan_handle_shift_out_of_bounds+0x29c/0x300 [] ? __ubsan_handle_load_invalid_value+0x1ba/0x1ba [] ? get_futex_key+0x4f9/0xf80 [] ? futex_wake_op+0x636/0xfc0 [] ? futex_lock_pi_atomic+0x2a0/0x2a0 [] ? futex_wake_op+0xce9/0xfc0 [] ? futex_wait_restart+0x240/0x240 [] ? do_futex+0x54e/0xb60 [] ? SyS_futex+0x138/0x2b0 Fix that by having FUTEX_OP_OPARG_SHIFT unsigned. Signed-off-by: Jiri Slaby --- include/uapi/linux/futex.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h index 0b1f716373c7..954a23b18e68 100644 --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -130,7 +130,7 @@ struct robust_list_head { #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */ #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */ -#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */ +#define FUTEX_OP_OPARG_SHIFT 8U /* Use (1 << OPARG) instead of OPARG. */ #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */ #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */ -- 2.10.1