From: Hugh Dickins Date: Mon, 2 Oct 2017 17:57:24 +0000 (-0700) Subject: kaiser: kaiser_remove_mapping() move along the pgd X-Git-Tag: v4.4.110~29 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f127705d26b34c053e59b47aef84b3ea564dd743;p=thirdparty%2Fkernel%2Fstable.git kaiser: kaiser_remove_mapping() move along the pgd When removing the bogus comment from kaiser_remove_mapping(), I really ought to have checked the extent of its bogosity: as Neel points out, there is nothing to stop unmap_pud_range_nofree() from continuing beyond the end of a pud (and starting in the wrong position on the next). Fix kaiser_remove_mapping() to constrain the extent and advance pgd pointer correctly: use pgd_addr_end() macro as used throughout base mm (but don't assume page-rounded start and size in this case). But this bug was very unlikely to trigger in this backport: since any buddy allocation is contained within a single pud extent, and we are not using vmapped stacks (and are only mapping one page of stack anyway): the only way to hit this bug here would be when freeing a large modified ldt. Signed-off-by: Hugh Dickins Acked-by: Jiri Kosina Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/mm/kaiser.c b/arch/x86/mm/kaiser.c index 34e1d48e13391..1d50c44ff6a75 100644 --- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -297,11 +297,13 @@ void kaiser_remove_mapping(unsigned long start, unsigned long size) extern void unmap_pud_range_nofree(pgd_t *pgd, unsigned long start, unsigned long end); unsigned long end = start + size; - unsigned long addr; + unsigned long addr, next; + pgd_t *pgd; - for (addr = start; addr < end; addr += PGDIR_SIZE) { - pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(addr)); - unmap_pud_range_nofree(pgd, addr, end); + pgd = native_get_shadow_pgd(pgd_offset_k(start)); + for (addr = start; addr < end; pgd++, addr = next) { + next = pgd_addr_end(addr, end); + unmap_pud_range_nofree(pgd, addr, next); } }