From: Mike Kravetz <mike.kravetz@oracle.com>
To: Rik van Riel <riel@surriel.com>
Cc: Edward Adam Davis <eadavis@qq.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, llvm@lists.linux.dev, muchun.song@linux.dev,
nathan@kernel.org, ndesaulniers@google.com,
syzbot+6ada951e7c0f7bc8a71e@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com, trix@redhat.com
Subject: Re: [PATCH] mm/hugetlb: fix null ptr defer in hugetlb_vma_lock_write
Date: Thu, 2 Nov 2023 19:37:37 -0700 [thread overview]
Message-ID: <20231103023737.GC3531@monkey> (raw)
In-Reply-To: <20231103022426.GA3531@monkey>
On 11/02/23 19:24, Mike Kravetz wrote:
>
> In the specific case causing the null-ptr-deref, the resv_map pointer
> (vm_private_data) is NULL.
Hi Rik,
In commit bf4916922c60 hugetlbfs: extend hugetlb_vma_lock to private VMAs,
it correctly says:
Extend the locking scheme used to protect shared hugetlb mappings from
truncate vs page fault races, in order to protect private hugetlb mappings
(with resv_map) against MADV_DONTNEED.
That qualification '(with resv_map)' caught my attention originally, and
I thought about it again while looking into this. We now cover the common
cases, but there are still quite a few cases where resv_map is NULL for
private mappings. In such cases, the race between MADV_DONTNEED and page
fault still exists. Is that a concern?
With a bit more work we 'could' make sure every hugetlb vma has a lock
to participate in this scheme.
Any thhoughts?
--
Mike Kravetz
next prev parent reply other threads:[~2023-11-03 2:37 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-29 9:27 [syzbot] [mm?] general protection fault " syzbot
2023-10-31 18:38 ` Rik van Riel
2023-11-02 12:15 ` Aleksandr Nogikh
2023-11-01 6:36 ` [PATCH] mm/hugetlb: fix null ptr defer " Edward Adam Davis
2023-11-01 14:27 ` Rik van Riel
2023-11-02 12:58 ` Edward Adam Davis
2023-11-02 23:29 ` kernel test robot
2023-11-02 23:29 ` kernel test robot
2023-11-03 0:56 ` Rik van Riel
2023-11-03 1:26 ` kernel test robot
2023-11-03 2:24 ` Mike Kravetz
2023-11-03 2:28 ` Mike Kravetz
2023-11-03 2:37 ` Mike Kravetz [this message]
2023-11-03 3:15 ` Rik van Riel
2023-11-03 4:31 ` Mike Kravetz
2023-11-08 3:22 ` Mike Kravetz
2023-11-02 13:46 ` Yin, Fengwei
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