From bbc60c18ed17df75270da504bbd8f7bc4a52d43d Mon Sep 17 00:00:00 2001 From: Michael Abd-El-Malek Date: Fri, 4 Apr 2008 02:33:48 -0700 Subject: [PATCH] xen: fix grant table bug fix memory corruption and crash due to mis-sized grant table. A PV OS has two grant table data structures: the grant table itself and a free list. The free list is composed of an array of pages, which grow dynamically as the guest OS requires more grants. While the grant table contains 8-byte entries, the free list contains 4-byte entries. So we have half as many pages in the free list than in the grant table. There was a bug in the free list allocation code. The free list was indexed as if it was the same size as the grant table. But it's only half as large. So memory got corrupted, and I was seeing crashes in the slab allocator later on. Taken from: http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/4018c0da3360 Signed-off-by: Michael Abd-El-Malek Signed-off-by: Mark McLoughlin Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Ingo Molnar --- drivers/xen/grant-table.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index ea94dbabf9a..d85dc6d41c2 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -381,11 +381,15 @@ EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback); static int grow_gnttab_list(unsigned int more_frames) { unsigned int new_nr_grant_frames, extra_entries, i; + unsigned int nr_glist_frames, new_nr_glist_frames; new_nr_grant_frames = nr_grant_frames + more_frames; extra_entries = more_frames * GREFS_PER_GRANT_FRAME; - for (i = nr_grant_frames; i < new_nr_grant_frames; i++) { + nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; + new_nr_glist_frames = + (new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; + for (i = nr_glist_frames; i < new_nr_glist_frames; i++) { gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC); if (!gnttab_list[i]) goto grow_nomem; @@ -407,7 +411,7 @@ static int grow_gnttab_list(unsigned int more_frames) return 0; grow_nomem: - for ( ; i >= nr_grant_frames; i--) + for ( ; i >= nr_glist_frames; i--) free_page((unsigned long) gnttab_list[i]); return -ENOMEM; } @@ -530,7 +534,7 @@ static int gnttab_expand(unsigned int req_entries) static int __devinit gnttab_init(void) { int i; - unsigned int max_nr_glist_frames; + unsigned int max_nr_glist_frames, nr_glist_frames; unsigned int nr_init_grefs; if (!is_running_on_xen()) @@ -543,15 +547,15 @@ static int __devinit gnttab_init(void) * grant reference free list on the current hypervisor. */ max_nr_glist_frames = (boot_max_nr_grant_frames * - GREFS_PER_GRANT_FRAME / - (PAGE_SIZE / sizeof(grant_ref_t))); + GREFS_PER_GRANT_FRAME / RPP); gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *), GFP_KERNEL); if (gnttab_list == NULL) return -ENOMEM; - for (i = 0; i < nr_grant_frames; i++) { + nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; + for (i = 0; i < nr_glist_frames; i++) { gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL); if (gnttab_list[i] == NULL) goto ini_nomem; -- 2.41.1