From 38bfcc165dda5f4284d7c218b91df9e144ddd88d Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 27 Feb 2018 14:07:12 +0100 Subject: [PATCH] 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 --- xen/common/grant_table.c | 67 ++++++++++++++++++++++++++++--- xen/include/asm-arm/grant_table.h | 5 +++ xen/include/asm-x86/grant_table.h | 10 ++++- 3 files changed, 75 insertions(+), 7 deletions(-) diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c index 43ec69d519..210de0f37c 100644 --- a/xen/common/grant_table.c +++ b/xen/common/grant_table.c @@ -1636,23 +1636,74 @@ 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(gt, 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(gt, 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; } /* @@ -2962,8 +3013,9 @@ 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++ ) @@ -3804,6 +3856,11 @@ int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn, rc = -EINVAL; } + if ( !rc && paging_mode_translate(d) && + !gfn_eq(gnttab_get_frame_gfn(gt, status, idx), INVALID_GFN) ) + rc = guest_physmap_remove_page(d, gnttab_get_frame_gfn(gt, status, idx), + *mfn, 0); + if ( !rc ) gnttab_set_frame_gfn(gt, status, idx, gfn); diff --git a/xen/include/asm-arm/grant_table.h b/xen/include/asm-arm/grant_table.h index f5361c7dcf..5b8994cbd5 100644 --- a/xen/include/asm-arm/grant_table.h +++ b/xen/include/asm-arm/grant_table.h @@ -73,6 +73,11 @@ static inline unsigned int gnttab_dom0_max(void) (gfn); \ } while ( 0 ) +#define gnttab_get_frame_gfn(gt, st, idx) ({ \ + _gfn((st) ? gnttab_status_gmfn(NULL, gt, idx) \ + : gnttab_shared_gmfn(NULL, gt, 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 3177d82b69..66e9742003 100644 --- a/xen/include/asm-x86/grant_table.h +++ b/xen/include/asm-x86/grant_table.h @@ -47,6 +47,12 @@ static inline unsigned int gnttab_dom0_max(void) #define gnttab_init_arch(gt) 0 #define gnttab_destroy_arch(gt) do {} while ( 0 ) #define gnttab_set_frame_gfn(gt, st, idx, gfn) do {} while ( 0 ) +#define gnttab_get_frame_gfn(gt, st, idx) ({ \ + unsigned long mfn_ = (st) ? gnttab_status_mfn(gt, idx) \ + : gnttab_shared_mfn(gt, 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 { \ @@ -63,11 +69,11 @@ static inline unsigned int gnttab_dom0_max(void) } 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) \ -- 2.39.5