From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33002) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBS39-0004fT-As for qemu-devel@nongnu.org; Mon, 28 Nov 2016 14:57:16 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cBS38-0001ov-8s for qemu-devel@nongnu.org; Mon, 28 Nov 2016 14:57:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6614) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cBS38-0001of-0X for qemu-devel@nongnu.org; Mon, 28 Nov 2016 14:57:14 -0500 From: Laszlo Ersek Date: Mon, 28 Nov 2016 20:57:01 +0100 Message-Id: <20161128195701.24912-3-lersek@redhat.com> In-Reply-To: <20161128195701.24912-1-lersek@redhat.com> References: <20161128195701.24912-1-lersek@redhat.com> Subject: [Qemu-devel] [PATCH for-2.8 2/2] loader: fix undefined behavior in rom_order_compare() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu devel list Cc: "Michael S. Tsirkin" , Alistair Francis , Paolo Bonzini , Peter Maydell 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 --- hw/core/loader.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/core/loader.c b/hw/core/loader.c index c0d645a87134..766e48f2aec2 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); } -- 2.9.2