[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.7] x86/mm: don't wrongly set page ownership
commit 4f34d9fa68afa66e691434ea9945f005d6d5cb18 Author: Jan Beulich <jbeulich@xxxxxxxx> AuthorDate: Tue Dec 12 15:03:34 2017 +0100 Commit: Jan Beulich <jbeulich@xxxxxxxx> CommitDate: Tue Dec 12 15:03:34 2017 +0100 x86/mm: don't wrongly set page ownership PV domains can obtain mappings of any pages owned by the correct domain, including ones that aren't actually assigned as "normal" RAM, but used by Xen internally. At the moment such "internal" pages marked as owned by a guest include pages used to track logdirty bits, as well as p2m pages and the "unpaged pagetable" for HVM guests. Since the PV memory management and shadow code conflict in their use of struct page_info fields, and since shadow code is being used for log-dirty handling for PV domains, pages coming from the shadow pool must, for PV domains, not have the domain set as their owner. While the change could be done conditionally for just the PV case in shadow code, do it unconditionally (and for consistency also for HAP), just to be on the safe side. There's one special case though for shadow code: The page table used for running a HVM guest in unpaged mode is subject to get_page() (in set_shadow_status()) and hence must have its owner set. This is XSA-248. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> Reviewed-by: Tim Deegan <tim@xxxxxxx> Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx> master commit: ff2a793e15bb0b6254bc849ef8e83e1c284c3583 master date: 2017-12-12 14:28:36 +0100 --- xen/arch/x86/mm/hap/hap.c | 23 ++++++++++----------- xen/arch/x86/mm/shadow/common.c | 44 +++++++++++++++++++++++++++++------------ 2 files changed, 43 insertions(+), 24 deletions(-) diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c index 9c2cd49..8058a2f 100644 --- a/xen/arch/x86/mm/hap/hap.c +++ b/xen/arch/x86/mm/hap/hap.c @@ -283,8 +283,7 @@ static struct page_info *hap_alloc_p2m_page(struct domain *d) { d->arch.paging.hap.total_pages--; d->arch.paging.hap.p2m_pages++; - page_set_owner(pg, d); - pg->count_info |= 1; + ASSERT(!page_get_owner(pg) && !(pg->count_info & PGC_count_mask)); } else if ( !d->arch.paging.p2m_alloc_failed ) { @@ -299,21 +298,23 @@ static struct page_info *hap_alloc_p2m_page(struct domain *d) static void hap_free_p2m_page(struct domain *d, struct page_info *pg) { + struct domain *owner = page_get_owner(pg); + /* This is called both from the p2m code (which never holds the * paging lock) and the log-dirty code (which always does). */ paging_lock_recursive(d); - ASSERT(page_get_owner(pg) == d); - /* Should have just the one ref we gave it in alloc_p2m_page() */ - if ( (pg->count_info & PGC_count_mask) != 1 ) { - HAP_ERROR("Odd p2m page %p count c=%#lx t=%"PRtype_info"\n", - pg, pg->count_info, pg->u.inuse.type_info); + /* Should still have no owner and count zero. */ + if ( owner || (pg->count_info & PGC_count_mask) ) + { + HAP_ERROR("d%d: Odd p2m page %"PRI_mfn" d=%d c=%lx t=%"PRtype_info"\n", + d->domain_id, mfn_x(page_to_mfn(pg)), + owner ? owner->domain_id : DOMID_INVALID, + pg->count_info, pg->u.inuse.type_info); WARN(); + pg->count_info &= ~PGC_count_mask; + page_set_owner(pg, NULL); } - pg->count_info &= ~PGC_count_mask; - /* Free should not decrement domain's total allocation, since - * these pages were allocated without an owner. */ - page_set_owner(pg, NULL); d->arch.paging.hap.p2m_pages--; d->arch.paging.hap.total_pages++; hap_free(d, page_to_mfn(pg)); diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c index 4b4d210..05826b8 100644 --- a/xen/arch/x86/mm/shadow/common.c +++ b/xen/arch/x86/mm/shadow/common.c @@ -1574,32 +1574,29 @@ shadow_alloc_p2m_page(struct domain *d) pg = mfn_to_page(shadow_alloc(d, SH_type_p2m_table, 0)); d->arch.paging.shadow.p2m_pages++; d->arch.paging.shadow.total_pages--; + ASSERT(!page_get_owner(pg) && !(pg->count_info & PGC_count_mask)); paging_unlock(d); - /* Unlike shadow pages, mark p2m pages as owned by the domain. - * Marking the domain as the owner would normally allow the guest to - * create mappings of these pages, but these p2m pages will never be - * in the domain's guest-physical address space, and so that is not - * believed to be a concern. */ - page_set_owner(pg, d); - pg->count_info |= 1; return pg; } static void shadow_free_p2m_page(struct domain *d, struct page_info *pg) { - ASSERT(page_get_owner(pg) == d); - /* Should have just the one ref we gave it in alloc_p2m_page() */ - if ( (pg->count_info & PGC_count_mask) != 1 ) + struct domain *owner = page_get_owner(pg); + + /* Should still have no owner and count zero. */ + if ( owner || (pg->count_info & PGC_count_mask) ) { - SHADOW_ERROR("Odd p2m page count c=%#lx t=%"PRtype_info"\n", + SHADOW_ERROR("d%d: Odd p2m page %"PRI_mfn" d=%d c=%lx t=%"PRtype_info"\n", + d->domain_id, mfn_x(page_to_mfn(pg)), + owner ? owner->domain_id : DOMID_INVALID, pg->count_info, pg->u.inuse.type_info); + pg->count_info &= ~PGC_count_mask; + page_set_owner(pg, NULL); } - pg->count_info &= ~PGC_count_mask; pg->u.sh.type = SH_type_p2m_table; /* p2m code reuses type-info */ - page_set_owner(pg, NULL); /* This is called both from the p2m code (which never holds the * paging lock) and the log-dirty code (which always does). */ @@ -3218,7 +3215,9 @@ int shadow_enable(struct domain *d, u32 mode) | _PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE); unmap_domain_page(e); + pg->count_info = 1; pg->u.inuse.type_info = PGT_l2_page_table | 1 | PGT_validated; + page_set_owner(pg, d); } paging_lock(d); @@ -3256,7 +3255,11 @@ int shadow_enable(struct domain *d, u32 mode) if ( rv != 0 && !pagetable_is_null(p2m_get_pagetable(p2m)) ) p2m_teardown(p2m); if ( rv != 0 && pg != NULL ) + { + pg->count_info &= ~PGC_count_mask; + page_set_owner(pg, NULL); shadow_free_p2m_page(d, pg); + } domain_unpause(d); return rv; } @@ -3365,7 +3368,22 @@ out: /* Must be called outside the lock */ if ( unpaged_pagetable ) + { + if ( page_get_owner(unpaged_pagetable) == d && + (unpaged_pagetable->count_info & PGC_count_mask) == 1 ) + { + unpaged_pagetable->count_info &= ~PGC_count_mask; + page_set_owner(unpaged_pagetable, NULL); + } + /* Complain here in cases where shadow_free_p2m_page() won't. */ + else if ( !page_get_owner(unpaged_pagetable) && + !(unpaged_pagetable->count_info & PGC_count_mask) ) + SHADOW_ERROR("d%d: Odd unpaged pt %"PRI_mfn" c=%lx t=%"PRtype_info"\n", + d->domain_id, mfn_x(page_to_mfn(unpaged_pagetable)), + unpaged_pagetable->count_info, + unpaged_pagetable->u.inuse.type_info); shadow_free_p2m_page(d, unpaged_pagetable); + } } void shadow_final_teardown(struct domain *d) -- generated by git-patchbot for /home/xen/git/xen.git#stable-4.7 _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/xen-changelog
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