From: Qian Cai <cai@lca.pw>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andrew Morton <akpm@linux-foundation.org>,
elver@google.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, peterz@infradead.org,
syzbot+c034966b0b02f94f7f34@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH -next] fork: annotate a data race in vm_area_dup()
Date: Tue, 18 Feb 2020 07:40:06 -0500 [thread overview]
Message-ID: <93E6B243-9A0F-410C-8EE4-9D57E28AF5AF@lca.pw> (raw)
In-Reply-To: <20200218103002.6rtjreyqjepo3yxe@box>
> On Feb 18, 2020, at 5:29 AM, Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> I think I've got this:
>
> vm_area_dup() blindly copies all fields of orignal VMA to the new one.
> This includes coping vm_area_struct::shared.rb which is normally protected
> by i_mmap_lock. But this is fine because the read value will be
> overwritten on the following __vma_link_file() under proper protectection.
Right, multiple processes could share the same file-based address space where those vma have been linked into address_space::i_mmap via vm_area_struct::shared.rb. Thus, the reader could see its shared.rb linkage pointers got updated by other processes.
>
> So the fix is correct, but justificaiton is lacking.
>
> Also, I would like to more fine-grained annotation: marking with
> data_race() 200 bytes copy may hide other issues.
That is the harder part where I don’t think we have anything for that today. Macro, any suggestions? ASSERT_IGNORE_FIELD()?
next prev parent reply other threads:[~2020-02-18 12:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 20:33 [PATCH -next] fork: annotate a data race in vm_area_dup() Qian Cai
2020-02-17 22:31 ` Kirill A. Shutemov
2020-02-18 3:59 ` Qian Cai
2020-02-18 10:30 ` Kirill A. Shutemov
2020-02-18 12:40 ` Qian Cai [this message]
2020-02-18 14:09 ` Marco Elver
2020-02-18 15:00 ` Qian Cai
2020-02-18 15:18 ` Kirill A. Shutemov
2020-02-18 16:46 ` Qian Cai
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