From nobody Sun May 5 22:32:16 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1643319086080136.18173040765203; Thu, 27 Jan 2022 13:31:26 -0800 (PST) Received: from localhost ([::1]:51016 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nDCMV-00011s-VG for importer@patchew.org; Thu, 27 Jan 2022 16:31:23 -0500 Received: from eggs.gnu.org ([209.51.188.92]:40342) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nDCJg-0007Ou-Ba for qemu-devel@nongnu.org; Thu, 27 Jan 2022 16:28:29 -0500 Received: from vmicros1.altlinux.org ([194.107.17.57]:44974) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nDCJe-0001ht-9I for qemu-devel@nongnu.org; Thu, 27 Jan 2022 16:28:28 -0500 Received: from imap.altlinux.org (imap.altlinux.org [194.107.17.38]) by vmicros1.altlinux.org (Postfix) with ESMTP id 7EDBB72C8FA; Fri, 28 Jan 2022 00:28:23 +0300 (MSK) Received: from beacon.altlinux.org (unknown [193.43.10.9]) by imap.altlinux.org (Postfix) with ESMTPSA id 648F44A46F0; Fri, 28 Jan 2022 00:28:23 +0300 (MSK) From: Vitaly Chikunov To: Greg Kurz , Christian Schoenebeck , qemu-devel@nongnu.org Subject: [PATCH] 9pfs: Fix segfault in do_readdir_many caused by struct dirent overread Date: Fri, 28 Jan 2022 00:27:34 +0300 Message-Id: <20220127212734.218900-1-vt@altlinux.org> X-Mailer: git-send-email 2.33.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=194.107.17.57; envelope-from=vt@altlinux.org; helo=vmicros1.altlinux.org X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vitaly Chikunov , ldv@altlinux.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZM-MESSAGEID: 1643319089072100001 Content-Type: text/plain; charset="utf-8" `struct dirent' returned from readdir(3) could be shorter than `sizeof(struct dirent)', thus memcpy of sizeof length will overread into unallocated page causing SIGSEGV. Example stack trace: #0 0x00005555559ebeed v9fs_co_readdir_many (/usr/bin/qemu-system-x86_64 += 0x497eed) #1 0x00005555559ec2e9 v9fs_readdir (/usr/bin/qemu-system-x86_64 + 0x4982e= 9) #2 0x0000555555eb7983 coroutine_trampoline (/usr/bin/qemu-system-x86_64 += 0x963983) #3 0x00007ffff73e0be0 n/a (n/a + 0x0) Resolves: https://gitlab.com/qemu-project/qemu/-/issues/841 Signed-off-by: Vitaly Chikunov --- Tested on x86-64 Linux. hw/9pfs/codir.c | 7 +++++-- include/qemu/osdep.h | 6 ++++++ util/osdep.c | 23 +++++++++++++++++++++++ 3 files changed, 34 insertions(+), 2 deletions(-) diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c index 032cce04c4..ea7f5e6578 100644 --- a/hw/9pfs/codir.c +++ b/hw/9pfs/codir.c @@ -143,8 +143,11 @@ static int do_readdir_many(V9fsPDU *pdu, V9fsFidState = *fidp, } else { e =3D e->next =3D g_malloc0(sizeof(V9fsDirEnt)); } - e->dent =3D g_malloc0(sizeof(struct dirent)); - memcpy(e->dent, dent, sizeof(struct dirent)); + e->dent =3D qemu_dirent_dup(dent); + if (!e->dent) { + err =3D -errno; + break; + } =20 /* perform a full stat() for directory entry if requested by calle= r */ if (dostat) { diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h index d1660d67fa..b54d22db04 100644 --- a/include/qemu/osdep.h +++ b/include/qemu/osdep.h @@ -805,6 +805,12 @@ static inline int platform_does_not_support_system(con= st char *command) } #endif /* !HAVE_SYSTEM_FUNCTION */ =20 +/** + * Actual 'struct dirent' size may be bigger or shorter than + * sizeof(struct dirent) in many cases. + */ +struct dirent *qemu_dirent_dup(struct dirent *dent); + #ifdef __cplusplus } #endif diff --git a/util/osdep.c b/util/osdep.c index 42a0a4986a..e39d1071fd 100644 --- a/util/osdep.c +++ b/util/osdep.c @@ -33,6 +33,7 @@ extern int madvise(char *, size_t, int); #endif =20 +#include #include "qemu-common.h" #include "qemu/cutils.h" #include "qemu/sockets.h" @@ -615,3 +616,25 @@ writev(int fd, const struct iovec *iov, int iov_cnt) return readv_writev(fd, iov, iov_cnt, true); } #endif + +struct dirent * +qemu_dirent_dup(struct dirent *dent) +{ + struct dirent *dst; +#if defined _DIRENT_HAVE_D_RECLEN + /* Avoid use of strlen() if there's d_reclen. */ + dst =3D g_malloc(dent->d_reclen); +#else + /* Fallback to a most portable way. */ + const size_t reclen =3D offsetof(struct dirent, d_name) + strlen(dent-= >d_name) + 1; + + dst =3D g_malloc(reclen); +#endif + if (!dst) + return NULL; +#ifdef _DIRENT_HAVE_D_RECLEN + return memcpy(dst, dent, dent->d_reclen); +#else + return memcpy(dst, dent, reclen); +#endif +} --=20 2.33.0