From 8c47f86fb53485e298ed154eb5c0ca0a89b85a24 Mon Sep 17 00:00:00 2001 From: Carsten Otte Date: Wed, 4 Feb 2009 15:12:16 -0800 Subject: [PATCH] do_wp_page: fix regression with execute in place commit ab92661d5d9514647346047f30f67a7f35ffea67 upstream. Fix do_wp_page for VM_MIXEDMAP mappings. In the case where pfn_valid returns 0 for a pfn at the beginning of do_wp_page and the mapping is not shared writable, the code branches to label `gotten:' with old_page == NULL. In case the vma is locked (vma->vm_flags & VM_LOCKED), lock_page, clear_page_mlock, and unlock_page try to access the old_page. This patch checks whether old_page is valid before it is dereferenced. The regression was introduced by "mlock: mlocked pages are unevictable" (commit b291f000393f5a0b679012b39d79fbc85c018233). Signed-off-by: Carsten Otte Cc: Nick Piggin Cc: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index 164951c47305..fe2257f9ac80 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1881,7 +1881,7 @@ gotten: * Don't let another task, with possibly unlocked vma, * keep the mlocked page. */ - if (vma->vm_flags & VM_LOCKED) { + if ((vma->vm_flags & VM_LOCKED) && old_page) { lock_page(old_page); /* for LRU manipulation */ clear_page_mlock(old_page); unlock_page(old_page); -- 2.39.5