From: Jan Beulich Date: Tue, 27 Feb 2018 13:28:36 +0000 (+0100) Subject: gnttab: don't blindly free status pages upon version change X-Git-Tag: RELEASE-4.8.4~101 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=141be845d96614e3ebe39237368a70fe794b21be;p=people%2Fandrewcoop%2Fxen.git gnttab: don't blindly free status pages upon version change There may still be active mappings, which would trigger the respective BUG_ON(). Split the loop into one dealing with the page attributes and the second (when the first fully passed) freeing the pages. Return an error if any pages still have pending references. This is part of XSA-255. Signed-off-by: Jan Beulich Reviewed-by: Stefano Stabellini Reviewed-by: Andrew Cooper master commit: 38bfcc165dda5f4284d7c218b91df9e144ddd88d master date: 2018-02-27 14:07:12 +0100 --- diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index 591cfd870e..4c1a407c95 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -1182,12 +1182,22 @@ int xenmem_add_to_physmap_one( mfn = mfn_x(INVALID_MFN); } + if ( mfn != mfn_x(INVALID_MFN) && + !gfn_eq(gnttab_get_frame_gfn(d, status, idx), INVALID_GFN) ) + { + rc = guest_physmap_remove_page(d, + gnttab_get_frame_gfn(d, status, idx), + _mfn(mfn), 0); + if ( rc ) + { + grant_write_unlock(d->grant_table); + return rc; + } + } + if ( mfn != mfn_x(INVALID_MFN) ) { - if ( status ) - d->arch.grant_status_gfn[idx] = gfn; - else - d->arch.grant_shared_gfn[idx] = gfn; + gnttab_set_frame_gfn(d, status, idx, gfn); t = p2m_ram_rw; } diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index 32d093f6e9..58cad3a6d4 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -1516,23 +1516,74 @@ status_alloc_failed: return -ENOMEM; } -static void +static int gnttab_unpopulate_status_frames(struct domain *d, struct grant_table *gt) { - int i; + unsigned int i; for ( i = 0; i < nr_status_frames(gt); i++ ) { struct page_info *pg = virt_to_page(gt->status[i]); + gfn_t gfn = gnttab_get_frame_gfn(d, true, i); + + /* + * For translated domains, recovering from failure after partial + * changes were made is more complicated than it seems worth + * implementing at this time. Hence respective error paths below + * crash the domain in such a case. + */ + if ( paging_mode_translate(d) ) + { + int rc = gfn_eq(gfn, INVALID_GFN) + ? 0 + : guest_physmap_remove_page(d, gfn, + _mfn(page_to_mfn(pg)), 0); + + if ( rc ) + { + gprintk(XENLOG_ERR, + "Could not remove status frame %u (GFN %#lx) from P2M\n", + i, gfn_x(gfn)); + domain_crash(d); + return rc; + } + gnttab_set_frame_gfn(d, true, i, INVALID_GFN); + } BUG_ON(page_get_owner(pg) != d); if ( test_and_clear_bit(_PGC_allocated, &pg->count_info) ) put_page(pg); - BUG_ON(pg->count_info & ~PGC_xen_heap); + + if ( pg->count_info & ~PGC_xen_heap ) + { + if ( paging_mode_translate(d) ) + { + gprintk(XENLOG_ERR, + "Wrong page state %#lx of status frame %u (GFN %#lx)\n", + pg->count_info, i, gfn_x(gfn)); + domain_crash(d); + } + else + { + if ( get_page(pg, d) ) + set_bit(_PGC_allocated, &pg->count_info); + while ( i-- ) + gnttab_create_status_page(d, gt, i); + } + return -EBUSY; + } + + page_set_owner(pg, NULL); + } + + for ( i = 0; i < nr_status_frames(gt); i++ ) + { free_xenheap_page(gt->status[i]); gt->status[i] = NULL; } gt->nr_status_frames = 0; + + return 0; } /* @@ -2774,8 +2825,9 @@ gnttab_set_version(XEN_GUEST_HANDLE_PARAM(gnttab_set_version_t) uop) break; } - if ( op.version < 2 && gt->gt_version == 2 ) - gnttab_unpopulate_status_frames(currd, gt); + if ( op.version < 2 && gt->gt_version == 2 && + (res = gnttab_unpopulate_status_frames(currd, gt)) != 0 ) + goto out_unlock; /* Make sure there's no crud left over from the old version. */ for ( i = 0; i < nr_grant_frames(gt); i++ ) diff --git a/xen/include/asm-arm/grant_table.h b/xen/include/asm-arm/grant_table.h index 4d576c5905..2f9224fb7a 100644 --- a/xen/include/asm-arm/grant_table.h +++ b/xen/include/asm-arm/grant_table.h @@ -20,6 +20,17 @@ static inline int replace_grant_supported(void) return 1; } +#define gnttab_set_frame_gfn(d, st, idx, gfn) \ + do { \ + ((st) ? (d)->arch.grant_status_gfn \ + : (d)->arch.grant_shared_gfn)[idx] = (gfn); \ + } while ( 0 ) + +#define gnttab_get_frame_gfn(d, st, idx) ({ \ + _gfn((st) ? gnttab_status_gmfn(d, (d)->grant_table, idx) \ + : gnttab_shared_gmfn(d, (d)->grant_table, idx)); \ +}) + #define gnttab_create_shared_page(d, t, i) \ do { \ share_xen_page_with_guest( \ diff --git a/xen/include/asm-x86/grant_table.h b/xen/include/asm-x86/grant_table.h index 9ca631c4e3..9c64361ee2 100644 --- a/xen/include/asm-x86/grant_table.h +++ b/xen/include/asm-x86/grant_table.h @@ -18,6 +18,14 @@ int create_grant_host_mapping(uint64_t addr, unsigned long frame, int replace_grant_host_mapping( uint64_t addr, unsigned long frame, uint64_t new_addr, unsigned int flags); +#define gnttab_set_frame_gfn(d, st, idx, gfn) do {} while ( 0 ) +#define gnttab_get_frame_gfn(d, st, idx) ({ \ + unsigned long mfn_ = (st) ? gnttab_status_mfn((d)->grant_table, idx) \ + : gnttab_shared_mfn((d)->grant_table, idx); \ + unsigned long gpfn_ = get_gpfn_from_mfn(mfn_); \ + VALID_M2P(gpfn_) ? _gfn(gpfn_) : INVALID_GFN; \ +}) + #define gnttab_create_shared_page(d, t, i) \ do { \ share_xen_page_with_guest( \ @@ -33,11 +41,11 @@ int replace_grant_host_mapping( } while ( 0 ) -#define gnttab_shared_mfn(d, t, i) \ +#define gnttab_shared_mfn(t, i) \ ((virt_to_maddr((t)->shared_raw[i]) >> PAGE_SHIFT)) #define gnttab_shared_gmfn(d, t, i) \ - (mfn_to_gmfn(d, gnttab_shared_mfn(d, t, i))) + (mfn_to_gmfn(d, gnttab_shared_mfn(t, i))) #define gnttab_status_mfn(t, i) \