From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 707BA6B0292 for ; Tue, 20 Jun 2017 05:10:47 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id 33so111224440pgx.14 for ; Tue, 20 Jun 2017 02:10:47 -0700 (PDT) Received: from mail-pf0-x235.google.com (mail-pf0-x235.google.com. [2607:f8b0:400e:c00::235]) by mx.google.com with ESMTPS id f2si9864646pgc.108.2017.06.20.02.10.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Jun 2017 02:10:46 -0700 (PDT) Received: by mail-pf0-x235.google.com with SMTP id c73so6320458pfk.2 for ; Tue, 20 Jun 2017 02:10:46 -0700 (PDT) Date: Tue, 20 Jun 2017 02:10:44 -0700 (PDT) From: Hugh Dickins Subject: [PATCH] mm: fix new crash in unmapped_area_topdown() Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Dave Jones , Oleg Nesterov , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Trinity gets kernel BUG at mm/mmap.c:1963! in about 3 minutes of mmap testing. That's the VM_BUG_ON(gap_end < gap_start) at the end of unmapped_area_topdown(). Linus points out how MAP_FIXED (which does not have to respect our stack guard gap intentions) could result in gap_end below gap_start there. Fix that, and the similar case in its alternative, unmapped_area(). Cc: stable@vger.kernel.org Fixes: 1be7107fbe18 ("mm: larger stack guard gap, between vmas") Reported-by: Dave Jones Debugged-by: Linus Torvalds Signed-off-by: Hugh Dickins --- mm/mmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- 4.12-rc6/mm/mmap.c 2017-06-19 09:06:10.035407505 -0700 +++ linux/mm/mmap.c 2017-06-19 21:09:28.616707311 -0700 @@ -1817,7 +1817,8 @@ unsigned long unmapped_area(struct vm_un /* Check if current node has a suitable gap */ if (gap_start > high_limit) return -ENOMEM; - if (gap_end >= low_limit && gap_end - gap_start >= length) + if (gap_end >= low_limit && + gap_end > gap_start && gap_end - gap_start >= length) goto found; /* Visit right subtree if it looks promising */ @@ -1920,7 +1921,8 @@ unsigned long unmapped_area_topdown(stru gap_end = vm_start_gap(vma); if (gap_end < low_limit) return -ENOMEM; - if (gap_start <= high_limit && gap_end - gap_start >= length) + if (gap_start <= high_limit && + gap_end > gap_start && gap_end - gap_start >= length) goto found; /* Visit left subtree if it looks promising */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org