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[86.183.162.242]) by smtp.gmail.com with ESMTPSA id x128sm4637293wmb.29.2021.01.19.04.45.31 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 Jan 2021 04:45:32 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 9e10f23a-a1b5-4543-b2ed-502fe36bc803 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:reply-to:to:cc:references:in-reply-to:subject:date:message-id :mime-version:content-transfer-encoding:thread-index :content-language; bh=Ua4wIn6UjicH7b6kEbqGScS2U01j/xJHt0R8vSGbkSQ=; b=qexrHV60CigLsqvJODRfZG6PrcbTwRuuhDxsbNetZTnvRznTCKnUd/MctfzNbg9p2k 4X2ArnII13UmDTXSioyTFr7mD8UMOuXRcVwLGgNfoUyYOiURWDn5uKMKCIpXJMfDqZ6F KaA86bwqvOa0Grr+mlGTjaudbk7Z0PPzmUZM72EKcntdu+qQkQcv1nu8O6Tw6IaRbGbX ewhZPrBNh75KTP51Ci3TFDflpvzbYhHczNeZP12orgLVmVjg77B9NkZBk8Ukd1sgCyXc VbZYOuXWgAYOtR9DiilkHmCNMO5gboh0cxrNRlsbolBwk4MOvQgwHuY3e2yRVXHvdB7/ jQ5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:reply-to:to:cc:references:in-reply-to :subject:date:message-id:mime-version:content-transfer-encoding :thread-index:content-language; bh=Ua4wIn6UjicH7b6kEbqGScS2U01j/xJHt0R8vSGbkSQ=; b=SNbwyIKTPlYRCnwbsb36OFzcb7lEObCmfBjsHe2UFvqb3NdKVpOVpDljURA1slzpg+ bMY+2IGktGDXz+LWEvJPMQ3FuzHVgg/QogV1LcvZidaAADRWzoNISiI5JJ0jRiC+zNUG ejOI1JDofw4EvBBDExq+l6EpABU8qYlG8dAZTQm4lEB5Tii0gWMlIixGWS46DTxMvADv nzuSzMdclB7nxB7xJJRBmoiter8pd0KB4rQR+vfTfei3hmMIELR1BbQIIXT6sUKSGV4/ RcUAlGYaTsMb0OgRYvD7lQvRr5YYT8N81eUOQteUqaa0o9SDpuN98pMGjcaetue0WEDA zB5w== X-Gm-Message-State: AOAM5316sWZmmAtB2UAXZftHplN2gIz6FSJ9XC69cz2tBx1i+mBNAJ7S 9K88dSg2zu0C3Yma02U+Qyk= X-Google-Smtp-Source: ABdhPJwC55kXx6QMg5U6187pexcfKUtjiiqY7shBGz2yHt2/hLsBT75biW97ybAvpratMPHr+yeo2A== X-Received: by 2002:a5d:5512:: with SMTP id b18mr4250928wrv.13.1611060332752; Tue, 19 Jan 2021 04:45:32 -0800 (PST) From: Paul Durrant X-Google-Original-From: "Paul Durrant" Reply-To: To: "'Andrew Cooper'" , "'Xen-devel'" Cc: "'Jan Beulich'" , =?utf-8?Q?'Roger_Pau_Monn=C3=A9'?= , "'Wei Liu'" , "'Tamas K Lengyel'" References: <20210119094122.23713-1-andrew.cooper3@citrix.com> <20210119122756.27772-1-andrew.cooper3@citrix.com> In-Reply-To: <20210119122756.27772-1-andrew.cooper3@citrix.com> Subject: RE: [PATCH v2] x86/mm: Short circuit damage from "fishy" ref/typecount failure Date: Tue, 19 Jan 2021 12:45:31 -0000 Message-ID: <010d01d6ee60$f958b620$ec0a2260$@xen.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQGBGS7bP+6FoZJgIsckysiPtkyajgKXs/fwqsXRqBA= Content-Language: en-gb > -----Original Message----- > From: Andrew Cooper > Sent: 19 January 2021 12:28 > To: Xen-devel > Cc: Andrew Cooper ; Jan Beulich = ; Roger Pau Monn=C3=A9 > ; Wei Liu ; Paul Durrant = ; Tamas K Lengyel > > Subject: [PATCH v2] x86/mm: Short circuit damage from "fishy" = ref/typecount failure >=20 > This code has been copied in 3 places, but it is problematic. >=20 > All cases will hit a BUG() later in domain teardown, when a the = missing > type/count reference is underflowed. >=20 > Don't complicated the logic by leaving a totally unqualified domain = crash, and > a timebomb which will be triggered by the toolstack at a slightly = later, and > seemingly unrelated, point. >=20 > Signed-off-by: Andrew Cooper > --- > CC: Jan Beulich > CC: Roger Pau Monn=C3=A9 > CC: Wei Liu > CC: Paul Durrant > CC: Tamas K Lengyel >=20 > v2: > * Reword the commit message. > * Switch BUG() to BUG_ON() to further reduce code volume. > --- > xen/arch/x86/hvm/ioreq.c | 11 ++--------- > xen/arch/x86/hvm/vmx/vmx.c | 11 ++--------- > xen/arch/x86/mm/mem_paging.c | 17 ++++------------- > 3 files changed, 8 insertions(+), 31 deletions(-) >=20 > diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c > index 1cc27df87f..0c38cfa151 100644 > --- a/xen/arch/x86/hvm/ioreq.c > +++ b/xen/arch/x86/hvm/ioreq.c > @@ -366,15 +366,8 @@ static int hvm_alloc_ioreq_mfn(struct = hvm_ioreq_server *s, bool buf) > if ( !page ) > return -ENOMEM; >=20 > - if ( !get_page_and_type(page, s->target, PGT_writable_page) ) > - { > - /* > - * The domain can't possibly know about this page yet, so = failure > - * here is a clear indication of something fishy going on. > - */ > - domain_crash(s->emulator); > - return -ENODATA; > - } > + /* Domain can't know about this page yet - something fishy going = on. */ > + BUG_ON(!get_page_and_type(page, s->target, PGT_writable_page)); >=20 > iorp->va =3D __map_domain_page_global(page); > if ( !iorp->va ) > diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c > index 2d4475ee3d..8e438cb781 100644 > --- a/xen/arch/x86/hvm/vmx/vmx.c > +++ b/xen/arch/x86/hvm/vmx/vmx.c > @@ -3042,15 +3042,8 @@ static int vmx_alloc_vlapic_mapping(struct = domain *d) > if ( !pg ) > return -ENOMEM; >=20 > - if ( !get_page_and_type(pg, d, PGT_writable_page) ) > - { > - /* > - * The domain can't possibly know about this page yet, so = failure > - * here is a clear indication of something fishy going on. > - */ > - domain_crash(d); > - return -ENODATA; > - } > + /* Domain can't know about this page yet - something fishy going = on. */ > + BUG_ON(!get_page_and_type(page, s->target, PGT_writable_page)); Does this compile? s/page/pg s/s->target/d ...and similar below is needed AFAICT. Paul >=20 > mfn =3D page_to_mfn(pg); > clear_domain_page(mfn); > diff --git a/xen/arch/x86/mm/mem_paging.c = b/xen/arch/x86/mm/mem_paging.c > index 01281f786e..6e90019e76 100644 > --- a/xen/arch/x86/mm/mem_paging.c > +++ b/xen/arch/x86/mm/mem_paging.c > @@ -379,19 +379,10 @@ static int prepare(struct domain *d, gfn_t gfn, > page =3D alloc_domheap_page(d, 0); > if ( unlikely(page =3D=3D NULL) ) > goto out; > - if ( unlikely(!get_page(page, d)) ) > - { > - /* > - * The domain can't possibly know about this page yet, so = failure > - * here is a clear indication of something fishy going = on. > - */ > - gprintk(XENLOG_ERR, > - "%pd: fresh page for GFN %"PRI_gfn" in unexpected = state\n", > - d, gfn_x(gfn)); > - domain_crash(d); > - page =3D NULL; > - goto out; > - } > + > + /* Domain can't know about this page yet - something fishy = going on. */ > + BUG_ON(!get_page(page, s->target)); > + > mfn =3D page_to_mfn(page); > page_extant =3D 0; >=20 > -- > 2.11.0