From 9b79022ca909b66e2cd0cfd9248f832fc165f77f Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 28 Jul 2008 17:54:21 -0700 Subject: [PATCH] Fix 'get_user_pages_fast()' with non-page-aligned start address Alexey Dobriyan reported trouble with LTP with the new fast-gup code, and Johannes Weiner debugged it to non-page-aligned addresses, where the new get_user_pages_fast() code would do all the wrong things, including just traversing past the end of the requested area due to 'addr' never matching 'end' exactly. This is not a pretty fix, and we may actually want to move the alignment into generic code, leaving just the core code per-arch, but Alexey verified that the vmsplice01 LTP test doesn't crash with this. Reported-and-tested-by: Alexey Dobriyan Debugged-by: Johannes Weiner Cc: Nick Piggin Cc: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86/mm/gup.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index 3085f25b435..007bb06c750 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -223,14 +223,17 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, struct page **pages) { struct mm_struct *mm = current->mm; - unsigned long end = start + (nr_pages << PAGE_SHIFT); - unsigned long addr = start; + unsigned long addr, len, end; unsigned long next; pgd_t *pgdp; int nr = 0; + start &= PAGE_MASK; + addr = start; + len = (unsigned long) nr_pages << PAGE_SHIFT; + end = start + len; if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ, - start, nr_pages*PAGE_SIZE))) + start, len))) goto slow_irqon; /* -- 2.41.1