From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41TVWT2pHQzF36c for ; Mon, 16 Jul 2018 14:17:57 +1000 (AEST) Date: Mon, 16 Jul 2018 14:17:50 +1000 From: David Gibson To: Alexey Kardashevskiy Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, "Aneesh Kumar K.V" , Alex Williamson , Michael Ellerman , Nicholas Piggin , Paul Mackerras , Balbir Singh Subject: Re: [PATCH kernel v6 2/2] KVM: PPC: Check if IOMMU page is contained in the pinned physical page Message-ID: <20180716041750.GG2599@umbus.fritz.box> References: <20180711110044.15939-1-aik@ozlabs.ru> <20180711110044.15939-3-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="9Iq5ULCa7nGtWwZS" In-Reply-To: <20180711110044.15939-3-aik@ozlabs.ru> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --9Iq5ULCa7nGtWwZS Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jul 11, 2018 at 09:00:44PM +1000, Alexey Kardashevskiy wrote: > A VM which has: > - a DMA capable device passed through to it (eg. network card); > - running a malicious kernel that ignores H_PUT_TCE failure; > - capability of using IOMMU pages bigger that physical pages > can create an IOMMU mapping that exposes (for example) 16MB of > the host physical memory to the device when only 64K was allocated to the= VM. >=20 > The remaining 16MB - 64K will be some other content of host memory, possi= bly > including pages of the VM, but also pages of host kernel memory, host > programs or other VMs. >=20 > The attacking VM does not control the location of the page it can map, > and is only allowed to map as many pages as it has pages of RAM. >=20 > We already have a check in drivers/vfio/vfio_iommu_spapr_tce.c that > an IOMMU page is contained in the physical page so the PCI hardware won't > get access to unassigned host memory; however this check is missing in > the KVM fastpath (H_PUT_TCE accelerated code). We were lucky so far and > did not hit this yet as the very first time when the mapping happens > we do not have tbl::it_userspace allocated yet and fall back to > the userspace which in turn calls VFIO IOMMU driver, this fails and > the guest does not retry, >=20 > This stores the smallest preregistered page size in the preregistered > region descriptor and changes the mm_iommu_xxx API to check this against > the IOMMU page size. >=20 > This calculates maximum page size as a minimum of the natural region > alignment and compound page size. For the page shift this uses the shift > returned by find_linux_pte() which indicates how the page is mapped to > the current userspace - if the page is huge and this is not a zero, then > it is a leaf pte and the page is mapped within the range. >=20 > Signed-off-by: Alexey Kardashevskiy Reviewed-by: David Gibson > --- > Changes: > v6: > * replaced hugetlbfs with pageshift from find_linux_pte() >=20 > v5: > * only consider compound pages from hugetlbfs >=20 > v4: > * reimplemented max pageshift calculation >=20 > v3: > * fixed upper limit for the page size > * added checks that we don't register parts of a huge page >=20 > v2: > * explicitely check for compound pages before calling compound_order() >=20 > --- > The bug is: run QEMU _without_ hugepages (no -mempath) and tell it to > advertise 16MB pages to the guest; a typical pseries guest will use 16MB > for IOMMU pages without checking the mmu pagesize and this will fail > at https://git.qemu.org/?p=3Dqemu.git;a=3Dblob;f=3Dhw/vfio/common.c;h=3Df= b396cf00ac40eb35967a04c9cc798ca896eed57;hb=3Drefs/heads/master#l256 >=20 > With the change, mapping will fail in KVM and the guest will print: >=20 > mlx5_core 0000:00:00.0: ibm,create-pe-dma-window(2027) 0 8000000 20000000= 18 1f returned 0 (liobn =3D 0x80000001 starting addr =3D 8000000 0) > mlx5_core 0000:00:00.0: created tce table LIOBN 0x80000001 for /pci@80000= 0020000000/ethernet@0 > mlx5_core 0000:00:00.0: failed to map direct window for /pci@800000020000= 000/ethernet@0: -1 > --- > arch/powerpc/include/asm/mmu_context.h | 4 ++-- > arch/powerpc/kvm/book3s_64_vio.c | 2 +- > arch/powerpc/kvm/book3s_64_vio_hv.c | 6 ++++-- > arch/powerpc/mm/mmu_context_iommu.c | 39 ++++++++++++++++++++++++++++= ++++-- > drivers/vfio/vfio_iommu_spapr_tce.c | 2 +- > 5 files changed, 45 insertions(+), 8 deletions(-) >=20 > diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/includ= e/asm/mmu_context.h > index 896efa5..79d570c 100644 > --- a/arch/powerpc/include/asm/mmu_context.h > +++ b/arch/powerpc/include/asm/mmu_context.h > @@ -35,9 +35,9 @@ extern struct mm_iommu_table_group_mem_t *mm_iommu_look= up_rm( > extern struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct= *mm, > unsigned long ua, unsigned long entries); > extern long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem, > - unsigned long ua, unsigned long *hpa); > + unsigned long ua, unsigned int pageshift, unsigned long *hpa); > extern long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem, > - unsigned long ua, unsigned long *hpa); > + unsigned long ua, unsigned int pageshift, unsigned long *hpa); > extern long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem); > extern void mm_iommu_mapped_dec(struct mm_iommu_table_group_mem_t *mem); > #endif > diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_6= 4_vio.c > index d066e37..8c456fa 100644 > --- a/arch/powerpc/kvm/book3s_64_vio.c > +++ b/arch/powerpc/kvm/book3s_64_vio.c > @@ -449,7 +449,7 @@ long kvmppc_tce_iommu_do_map(struct kvm *kvm, struct = iommu_table *tbl, > /* This only handles v2 IOMMU type, v1 is handled via ioctl() */ > return H_TOO_HARD; > =20 > - if (WARN_ON_ONCE(mm_iommu_ua_to_hpa(mem, ua, &hpa))) > + if (WARN_ON_ONCE(mm_iommu_ua_to_hpa(mem, ua, tbl->it_page_shift, &hpa))) > return H_HARDWARE; > =20 > if (mm_iommu_mapped_inc(mem)) > diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3= s_64_vio_hv.c > index 925fc31..5b298f5 100644 > --- a/arch/powerpc/kvm/book3s_64_vio_hv.c > +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c > @@ -279,7 +279,8 @@ static long kvmppc_rm_tce_iommu_do_map(struct kvm *kv= m, struct iommu_table *tbl, > if (!mem) > return H_TOO_HARD; > =20 > - if (WARN_ON_ONCE_RM(mm_iommu_ua_to_hpa_rm(mem, ua, &hpa))) > + if (WARN_ON_ONCE_RM(mm_iommu_ua_to_hpa_rm(mem, ua, tbl->it_page_shift, > + &hpa))) > return H_HARDWARE; > =20 > pua =3D (void *) vmalloc_to_phys(pua); > @@ -469,7 +470,8 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vc= pu, > =20 > mem =3D mm_iommu_lookup_rm(vcpu->kvm->mm, ua, IOMMU_PAGE_SIZE_4K); > if (mem) > - prereg =3D mm_iommu_ua_to_hpa_rm(mem, ua, &tces) =3D=3D 0; > + prereg =3D mm_iommu_ua_to_hpa_rm(mem, ua, > + IOMMU_PAGE_SHIFT_4K, &tces) =3D=3D 0; > } > =20 > if (!prereg) { > diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_co= ntext_iommu.c > index abb4364..0bb53a7 100644 > --- a/arch/powerpc/mm/mmu_context_iommu.c > +++ b/arch/powerpc/mm/mmu_context_iommu.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > =20 > static DEFINE_MUTEX(mem_list_mutex); > =20 > @@ -27,6 +28,7 @@ struct mm_iommu_table_group_mem_t { > struct rcu_head rcu; > unsigned long used; > atomic64_t mapped; > + unsigned int pageshift; > u64 ua; /* userspace address */ > u64 entries; /* number of entries in hpas[] */ > u64 *hpas; /* vmalloc'ed */ > @@ -125,6 +127,8 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long= ua, unsigned long entries, > { > struct mm_iommu_table_group_mem_t *mem; > long i, j, ret =3D 0, locked_entries =3D 0; > + unsigned int pageshift; > + unsigned long flags; > struct page *page =3D NULL; > =20 > mutex_lock(&mem_list_mutex); > @@ -159,6 +163,12 @@ long mm_iommu_get(struct mm_struct *mm, unsigned lon= g ua, unsigned long entries, > goto unlock_exit; > } > =20 > + /* > + * For a starting point for a maximum page size calculation > + * we use @ua and @entries natural alignment to allow IOMMU pages > + * smaller than huge pages but still bigger than PAGE_SIZE. > + */ > + mem->pageshift =3D __ffs(ua | (entries << PAGE_SHIFT)); > mem->hpas =3D vzalloc(array_size(entries, sizeof(mem->hpas[0]))); > if (!mem->hpas) { > kfree(mem); > @@ -199,6 +209,25 @@ long mm_iommu_get(struct mm_struct *mm, unsigned lon= g ua, unsigned long entries, > } > } > populate: > + pageshift =3D PAGE_SHIFT; > + if (PageCompound(page)) { > + pte_t *pte; > + struct page *head =3D compound_head(page); > + unsigned int compshift =3D compound_order(head); > + > + local_irq_save(flags); /* disables as well */ > + pte =3D find_linux_pte(mm->pgd, ua, NULL, &pageshift); > + local_irq_restore(flags); > + if (!pte) { > + ret =3D -EFAULT; > + goto unlock_exit; > + } > + /* Double check it is still the same pinned page */ > + if (pte_page(*pte) =3D=3D head && pageshift =3D=3D compshift) > + pageshift =3D max_t(unsigned int, pageshift, > + PAGE_SHIFT); > + } > + mem->pageshift =3D min(mem->pageshift, pageshift); > mem->hpas[i] =3D page_to_pfn(page) << PAGE_SHIFT; > } > =20 > @@ -349,7 +378,7 @@ struct mm_iommu_table_group_mem_t *mm_iommu_find(stru= ct mm_struct *mm, > EXPORT_SYMBOL_GPL(mm_iommu_find); > =20 > long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem, > - unsigned long ua, unsigned long *hpa) > + unsigned long ua, unsigned int pageshift, unsigned long *hpa) > { > const long entry =3D (ua - mem->ua) >> PAGE_SHIFT; > u64 *va =3D &mem->hpas[entry]; > @@ -357,6 +386,9 @@ long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_m= em_t *mem, > if (entry >=3D mem->entries) > return -EFAULT; > =20 > + if (pageshift > mem->pageshift) > + return -EFAULT; > + > *hpa =3D *va | (ua & ~PAGE_MASK); > =20 > return 0; > @@ -364,7 +396,7 @@ long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_m= em_t *mem, > EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa); > =20 > long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem, > - unsigned long ua, unsigned long *hpa) > + unsigned long ua, unsigned int pageshift, unsigned long *hpa) > { > const long entry =3D (ua - mem->ua) >> PAGE_SHIFT; > void *va =3D &mem->hpas[entry]; > @@ -373,6 +405,9 @@ long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_grou= p_mem_t *mem, > if (entry >=3D mem->entries) > return -EFAULT; > =20 > + if (pageshift > mem->pageshift) > + return -EFAULT; > + > pa =3D (void *) vmalloc_to_phys(va); > if (!pa) > return -EFAULT; > diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iomm= u_spapr_tce.c > index 2da5f05..7cd63b0 100644 > --- a/drivers/vfio/vfio_iommu_spapr_tce.c > +++ b/drivers/vfio/vfio_iommu_spapr_tce.c > @@ -467,7 +467,7 @@ static int tce_iommu_prereg_ua_to_hpa(struct tce_cont= ainer *container, > if (!mem) > return -EINVAL; > =20 > - ret =3D mm_iommu_ua_to_hpa(mem, tce, phpa); > + ret =3D mm_iommu_ua_to_hpa(mem, tce, shift, phpa); > if (ret) > return -EINVAL; > =20 --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. 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