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[2001:4830:134:3::11]) by mx.google.com with ESMTPS id f12si28338167qtc.72.2016.11.29.12.00.24 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 29 Nov 2016 12:00:24 -0800 (PST) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) client-ip=2001:4830:134:3::11; Authentication-Results: mx.google.com; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 2001:4830:134:3::11 as permitted sender) smtp.mailfrom=qemu-devel-bounces+patch=linaro.org@nongnu.org Received: from localhost ([::1]:39058 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBoZj-0000If-OX for patch@linaro.org; Tue, 29 Nov 2016 15:00:23 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57945) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBoVO-0006Ac-Tt for qemu-devel@nongnu.org; Tue, 29 Nov 2016 14:55:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cBoVL-0000WS-SP for qemu-devel@nongnu.org; Tue, 29 Nov 2016 14:55:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43832) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cBoVL-0000VB-K4 for qemu-devel@nongnu.org; Tue, 29 Nov 2016 14:55:51 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AB7B05455E; Tue, 29 Nov 2016 19:55:50 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-57.phx2.redhat.com [10.3.116.57]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id uATJtaE5030186; Tue, 29 Nov 2016 14:55:49 -0500 From: Laszlo Ersek To: qemu devel list Date: Tue, 29 Nov 2016 20:55:33 +0100 Message-Id: <20161129195533.23113-3-lersek@redhat.com> In-Reply-To: <20161129195533.23113-1-lersek@redhat.com> References: <20161129195533.23113-1-lersek@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 29 Nov 2016 19:55:50 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH for-2.8 v2 2/2] loader: fix undefined behavior in rom_order_compare() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Paolo Bonzini , Alistair Francis , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: "Qemu-devel" According to ISO C99 / N1256 (referenced in HACKING): > 6.5.8 Relational operators > > 4 For the purposes of these operators, a pointer to an object that is > not an element of an array behaves the same as a pointer to the first > element of an array of length one with the type of the object as its > element type. > > 5 When two pointers are compared, the result depends on the relative > locations in the address space of the objects pointed to. If two > pointers to object or incomplete types both point to the same object, > or both point one past the last element of the same array object, they > compare equal. If the objects pointed to are members of the same > aggregate object, pointers to structure members declared later compare > greater than pointers to members declared earlier in the structure, > and pointers to array elements with larger subscript values compare > greater than pointers to elements of the same array with lower > subscript values. All pointers to members of the same union object > compare equal. If the expression /P/ points to an element of an array > object and the expression /Q/ points to the last element of the same > array object, the pointer expression /Q+1/ compares greater than /P/. > In all other cases, the behavior is undefined. Our AddressSpace objects are allocated generally individually, and kept in the "address_spaces" linked list, so we mustn't compare their addresses with relops. Convert the pointers subjected to the relop in rom_order_compare() to "uintptr_t": > 7.18.1.4 Integer types capable of holding object pointers > > 1 [...] > > The following type designates an unsigned integer type with the > property that any valid pointer to void can be converted to this type, > then converted back to pointer to void, and the result will compare > equal to the original pointer: > > /uintptr_t/ > > These types are optional. Cc: "Michael S. Tsirkin" Cc: Alistair Francis Cc: Paolo Bonzini Cc: Peter Maydell Cc: qemu-devel@nongnu.org Fixes: 3e76099aacb4dae0d37ebf95305369e03d1491e6 Signed-off-by: Laszlo Ersek Reviewed-by: Alistair Francis --- Notes: v2: - fix checkpatch error (also verify with the script) - pick up R-b from Alistair hw/core/loader.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.9.2 diff --git a/hw/core/loader.c b/hw/core/loader.c index c0d645a87134..45742494e6fd 100644 --- a/hw/core/loader.c +++ b/hw/core/loader.c @@ -818,7 +818,7 @@ static QTAILQ_HEAD(, Rom) roms = QTAILQ_HEAD_INITIALIZER(roms); static inline bool rom_order_compare(Rom *rom, Rom *item) { - return (rom->as > item->as) || + return ((uintptr_t)(void *)rom->as > (uintptr_t)(void *)item->as) || (rom->as == item->as && rom->addr >= item->addr); }