From 08fa29d916c6e271ad13978cd993e7238c68db97 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Tue, 29 May 2012 15:06:15 -0700 Subject: [PATCH] mm: fix NULL ptr deref when walking hugepages A missing validation of the value returned by find_vma() could cause a NULL ptr dereference when walking the pagetable. This is triggerable from usermode by a simple user by trying to read a page info out of /proc/pid/pagemap which doesn't exist. Introduced by commit 025c5b2451e4 ("thp: optimize away unnecessary page table locking"). Signed-off-by: Sasha Levin Reviewed-by: Naoya Horiguchi Cc: David Rientjes Cc: Andi Kleen Cc: Andrea Arcangeli Cc: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki Cc: [3.4.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/task_mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 1030a716d155..7faaf2acc570 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -784,7 +784,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, /* find the first VMA at or above 'addr' */ vma = find_vma(walk->mm, addr); - if (pmd_trans_huge_lock(pmd, vma) == 1) { + if (vma && pmd_trans_huge_lock(pmd, vma) == 1) { for (; addr != end; addr += PAGE_SIZE) { unsigned long offset; -- 2.20.1