From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58853) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eXS7z-0003Qg-4a for qemu-devel@nongnu.org; Fri, 05 Jan 2018 08:33:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eXS7u-0004yo-Tx for qemu-devel@nongnu.org; Fri, 05 Jan 2018 08:33:43 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:42422 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eXS7u-0004yi-PY for qemu-devel@nongnu.org; Fri, 05 Jan 2018 08:33:38 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id w05DSvDR006220 for ; Fri, 5 Jan 2018 08:33:36 -0500 Received: from e16.ny.us.ibm.com (e16.ny.us.ibm.com [129.33.205.206]) by mx0b-001b2d01.pphosted.com with ESMTP id 2fa968jtvq-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 05 Jan 2018 08:33:36 -0500 Received: from localhost by e16.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 5 Jan 2018 08:33:35 -0500 From: Murilo Opsfelder Araujo Date: Fri, 5 Jan 2018 11:32:41 -0200 In-Reply-To: <20180105133241.14141-1-muriloo@linux.vnet.ibm.com> References: <20180105133241.14141-1-muriloo@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Message-Id: <20180105133241.14141-2-muriloo@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 1/1] block/nbd: fix segmentation fault when .desc is not null-terminated List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: qemu-block@nongnu.org, qemu-ppc@nongnu.org, Max Reitz , Kevin Wolf , Paolo Bonzini , Eric Blake , R Nageswara Sastry , Murilo Opsfelder Araujo The find_desc_by_name() from util/qemu-option.c relies on the .name not being NULL to call strcmp(). This check becomes unsafe when the list is not NULL-terminated, which is the case of nbd_runtime_opts in block/nbd.c, and can result in segmentation fault when strcmp() tries to access an invalid memory: #0 0x00007fff8c75f7d4 in __strcmp_power9 () from /lib64/libc.so.6 #1 0x00000000102d3ec8 in find_desc_by_name (desc=0x1036d6f0, name=0x28e46670 "server.path") at util/qemu-option.c:166 #2 0x00000000102d93e0 in qemu_opts_absorb_qdict (opts=0x28e47a80, qdict=0x28e469a0, errp=0x7fffec247c98) at util/qemu-option.c:1026 #3 0x000000001012a2e4 in nbd_open (bs=0x28e42290, options=0x28e469a0, flags=24578, errp=0x7fffec247d80) at block/nbd.c:406 #4 0x00000000100144e8 in bdrv_open_driver (bs=0x28e42290, drv=0x1036e070 , node_name=0x0, options=0x28e469a0, open_flags=24578, errp=0x7fffec247f50) at block.c:1135 #5 0x0000000010015b04 in bdrv_open_common (bs=0x28e42290, file=0x0, options=0x28e469a0, errp=0x7fffec247f50) at block.c:1395 >>From gdb, the desc[i].name was not NULL and resulted in strcmp() accessing an invalid memory: >>> p desc[5] $8 = { name = 0x1037f098 "R27A", type = 1561964883, help = 0xc0bbb23e , def_value_str = 0x2 } >>> p desc[6] $9 = { name = 0x103dac78 <__gcov0.do_qemu_init_bdrv_nbd_init> "\001", type = 272101528, help = 0x29ec0b754403e31f , def_value_str = 0x81f343b9 } This patch fixes the segmentation fault in strcmp() by adding a NULL element at the end of nbd_runtime_opts.desc list, which is the common practice to most of other structs like runtime_opts in block/null.c. Thus, the desc[i].name != NULL check becomes safe because it will not evaluate to true when .desc list reached its end. Reported-by: R. Nageswara Sastry Buglink: https://bugs.launchpad.net/qemu/+bug/1727259 Signed-off-by: Murilo Opsfelder Araujo --- block/nbd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/block/nbd.c b/block/nbd.c index a50d24b50a..8b8ba56cdd 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -388,6 +388,7 @@ static QemuOptsList nbd_runtime_opts = { .type = QEMU_OPT_STRING, .help = "ID of the TLS credentials to use", }, + { /* end of list */ } }, }; -- 2.14.3