From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BB567C433EF for ; Mon, 7 Feb 2022 16:34:04 +0000 (UTC) Received: from localhost ([::1]:43008 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nH6xn-00005D-Tm for qemu-devel@archiver.kernel.org; Mon, 07 Feb 2022 11:34:03 -0500 Received: from eggs.gnu.org ([209.51.188.92]:43598) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nH6th-00069G-GQ; Mon, 07 Feb 2022 11:29:49 -0500 Received: from kylie.crudebyte.com ([5.189.157.229]:35757) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nH6tf-0003iu-2U; Mon, 07 Feb 2022 11:29:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=crudebyte.com; s=kylie; h=Content-Type:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Content-ID:Content-Description; bh=Gqp295vnV5xOl3L4/csyFtzt8iiZTlVrp9YTEi649I0=; b=Yhn56qTQV9QjFHy5jux0w8pgs8 PvBBt1KhU1hjwNMf40p69n4Z5rhSzlXHIgmFEg8AUUP0zMLUlnquE2X1ZRKubOPIAfsRCOBzeMsBj 7tRCbfC8rh4xvyCatDncOsujnTjhm5wNa+M7qTPi0DsYVbRdQWcpIlo463lcFFK8cjq7Ns2fh6AMK 8V80nz65YbllHfe676hUtRZE1ZvYgcF+2LHLBbO/S4nDHa289N4YxLNqnI6fH2FoWHyDTD/vkA9L4 8ZOqHEvoKxq/EWX2hTPlIhNWsjcxrEJ1SRnI6/LQOqpHiPZ+QIEFc1fR9mrWqi8o29jfa7nbRgidJ Lg81wtk5hUC45YcErf5CiyFhJV0zUG1Mxcap4Rmamm6ysPulYyM/0jB77ogtcAOTXh+FOlQUBvsQf ld+LAf7/G0mk3xXEicpJU5reOxXkzrK/Nmw0fqIaE3TQaoS2p8UyEEPikE8tf6g1QDzkcXJRbMzqj ppWr/D1UxuD2xTKBoCX0Itqs/lpo9lDdXHCgIeeRlNI8BaVgACztS954rEE47F4Dz/1cWtozlyB6M XENAXAp9dDr2i7pNv2zu2Ouibr0bmgLxHLKrAbjNPS0ozfmtn5CYN87SYYVYgtzXb89MXBTkiYx2P +3p1+oDf2Jsn8dAW57XNZpsTjWdV/KElHJWKDpkVA=; From: Christian Schoenebeck To: qemu-devel@nongnu.org Cc: Greg Kurz , Vitaly Chikunov , "Dmitry V . Levin" , qemu-stable@nongnu.org, Philippe =?ISO-8859-1?Q?Mathieu=2DDaud=E9?= Subject: Re: [PATCH v4] 9pfs: Fix segfault in do_readdir_many caused by struct dirent overread Date: Mon, 07 Feb 2022 17:29:42 +0100 Message-ID: <2028775.f1p1aejyUC@silver> In-Reply-To: <20220207085607.426beff2@bahia> References: <20220206013419.849161-1-vt@altlinux.org> <20220207085607.426beff2@bahia> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Received-SPF: pass client-ip=5.189.157.229; envelope-from=qemu_oss@crudebyte.com; helo=kylie.crudebyte.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Montag, 7. Februar 2022 08:56:07 CET Greg Kurz wrote: > On Sun, 6 Feb 2022 04:34:19 +0300 > > Vitaly Chikunov wrote: > > `struct dirent' returned from readdir(3) could be shorter (or longer) > > 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 + 0x4982e9) #2 0x0000555555eb7983 > > coroutine_trampoline (/usr/bin/qemu-system-x86_64 + 0x963983) #3 > > 0x00007ffff73e0be0 n/a (n/a + 0x0) > > > > While fixing, provide a helper for any future `struct dirent' cloning. > > > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/841 > > Cc: qemu-stable@nongnu.org > > Co-authored-by: Christian Schoenebeck > > Reviewed-by: Dmitry V. Levin > > Signed-off-by: Vitaly Chikunov > > --- > > Tested on x68-64 Linux with btrfs-progs tests and slow qos-test. > > Changes since v3: > > - Update commentary on qemu_dirent_dup logic. > > - Use g_memdup as suggested by Greg Kurz. > > The synth driver should really be made compliant with the > _DIRENT_HAVE_D_* macros at some point, but this patch fixes > a crash and the comment is clear enough to understand the > sz == 0 weirdness so I won't object any further. > > Acked-by: Greg Kurz Reviewed-by: Christian Schoenebeck I wait a bit to see whether there are still objections by other people. Philippe maybe? > > hw/9pfs/codir.c | 3 +-- > > include/qemu/osdep.h | 13 +++++++++++++ > > util/osdep.c | 21 +++++++++++++++++++++ > > 3 files changed, 35 insertions(+), 2 deletions(-) > > > > diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c > > index 032cce04c4..c0873bde16 100644 > > --- a/hw/9pfs/codir.c > > +++ b/hw/9pfs/codir.c > > @@ -143,8 +143,7 @@ static int do_readdir_many(V9fsPDU *pdu, V9fsFidState > > *fidp,> > > } else { > > > > e = e->next = g_malloc0(sizeof(V9fsDirEnt)); > > > > } > > > > - e->dent = g_malloc0(sizeof(struct dirent)); > > - memcpy(e->dent, dent, sizeof(struct dirent)); > > + e->dent = qemu_dirent_dup(dent); > > > > /* perform a full stat() for directory entry if requested by > > caller */ > > if (dostat) { > > > > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > > index d1660d67fa..ce12f64853 100644 > > --- a/include/qemu/osdep.h > > +++ b/include/qemu/osdep.h > > @@ -805,6 +805,19 @@ static inline int > > platform_does_not_support_system(const char *command)> > > } > > #endif /* !HAVE_SYSTEM_FUNCTION */ > > > > +/** > > + * Duplicate directory entry @dent. > > + * > > + * It is highly recommended to use this function instead of open coding > > + * duplication of @c dirent objects, because the actual @c struct @c > > dirent + * size may be bigger or shorter than @c sizeof(struct dirent) > > and correct + * handling is platform specific (see gitlab issue #841). > > + * > > + * @dent - original directory entry to be duplicated > > + * @returns duplicated directory entry which should be freed with > > g_free() > > + */ > > +struct dirent *qemu_dirent_dup(struct dirent *dent); > > + > > > > #ifdef __cplusplus > > } > > #endif > > > > diff --git a/util/osdep.c b/util/osdep.c > > index 42a0a4986a..67fbf22778 100644 > > --- a/util/osdep.c > > +++ b/util/osdep.c > > @@ -33,6 +33,7 @@ > > > > extern int madvise(char *, size_t, int); > > #endif > > > > +#include > > > > #include "qemu-common.h" > > #include "qemu/cutils.h" > > #include "qemu/sockets.h" > > > > @@ -615,3 +616,23 @@ 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) > > +{ > > + size_t sz = 0; > > +#if defined _DIRENT_HAVE_D_RECLEN > > + /* Avoid use of strlen() if platform supports d_reclen. */ > > + sz = dent->d_reclen; > > +#endif > > + /* > > + * Test sz for zero even if d_reclen is available > > + * because some drivers may set d_reclen to zero. > > + */ > > + if (sz == 0) { > > + /* Fallback to the most portable way. */ > > + sz = offsetof(struct dirent, d_name) + > > + strlen(dent->d_name) + 1; > > + } > > + return g_memdup(dent, sz); > > +}