From 5bb2be127bb4ee2fa6fa4545ad68f084d3bc09b0 Mon Sep 17 00:00:00 2001 From: Ian Campbell Date: Fri, 11 Jan 2013 12:22:27 +0000 Subject: [PATCH] libxc: x86: ensure that the initial mapping fits into the guest's memory In particular we need to check that adding 512KB of slack and rounding up to a 4MB boundary do not overflow the guest's memory allocation. Otherwise we run off the end of the p2m when building the guest's initial page tables and populate them with garbage. Wei noticed this when build tiny (2MB) mini-os domains. Reported-by: Wei Liu Signed-off-by: Ian Campbell Acked-by: Jan Beulich Committed-by: Ian Campbell --- tools/libxc/xc_dom_core.c | 3 ++- tools/libxc/xc_dom_x86.c | 12 ++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/tools/libxc/xc_dom_core.c b/tools/libxc/xc_dom_core.c index 99f90dd45e..c8062d8773 100644 --- a/tools/libxc/xc_dom_core.c +++ b/tools/libxc/xc_dom_core.c @@ -873,7 +873,8 @@ int xc_dom_build_image(struct xc_dom_image *dom) goto err; if ( dom->arch_hooks->count_pgtables ) { - dom->arch_hooks->count_pgtables(dom); + if ( dom->arch_hooks->count_pgtables(dom) != 0 ) + goto err; if ( (dom->pgtables > 0) && (xc_dom_alloc_segment(dom, &dom->pgtables_seg, "page tables", 0, dom->pgtables * page_size) != 0) ) diff --git a/tools/libxc/xc_dom_x86.c b/tools/libxc/xc_dom_x86.c index 0cf1687718..240d7265fa 100644 --- a/tools/libxc/xc_dom_x86.c +++ b/tools/libxc/xc_dom_x86.c @@ -82,6 +82,7 @@ static int count_pgtables(struct xc_dom_image *dom, int pae, { int pages, extra_pages; xen_vaddr_t try_virt_end; + xen_pfn_t try_pfn_end; extra_pages = dom->alloc_bootstack ? 1 : 0; extra_pages += dom->extra_pages; @@ -91,6 +92,17 @@ static int count_pgtables(struct xc_dom_image *dom, int pae, { try_virt_end = round_up(dom->virt_alloc_end + pages * PAGE_SIZE_X86, bits_to_mask(22)); /* 4MB alignment */ + + try_pfn_end = (try_virt_end - dom->parms.virt_base) >> PAGE_SHIFT_X86; + + if ( try_pfn_end > dom->total_pages ) + { + xc_dom_panic(dom->xch, XC_OUT_OF_MEMORY, + "%s: not enough memory for initial mapping (%#"PRIpfn" > %#"PRIpfn")", + __FUNCTION__, try_pfn_end, dom->total_pages); + return -ENOMEM; + } + dom->pg_l4 = nr_page_tables(dom, dom->parms.virt_base, try_virt_end, l4_bits); dom->pg_l3 = -- 2.39.5