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Shutemov" To: Li Xinhai Cc: linux-mm@kvack.org, akpm@linux-foundation.org, Rik van Riel , "Kirill A. Shutemov" , Matthew Wilcox Subject: Re: [PATCH 1/3] mm: don't prepare anon_vma if vma has VM_WIPEONFORK Message-ID: <20200402134537.avk5p7247zqwp4cg@box> References: <1581150928-3214-1-git-send-email-lixinhai.lxh@gmail.com> <1581150928-3214-2-git-send-email-lixinhai.lxh@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1581150928-3214-2-git-send-email-lixinhai.lxh@gmail.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, Feb 08, 2020 at 08:35:26AM +0000, Li Xinhai wrote: > In dup_mmap(), anon_vma_prepare() is called for vma has VM_WIPEONFORK, > and parameter 'tmp' (i.e., the new vma of child) has same ->vm_next and > ->vm_prev as its parent vma. That allows anon_vma used by parent been > mistakenly shared by child (find_mergeable_anon_vma() will do this reuse > work). > > Besides this issue, call anon_vma_prepare() should be avoided because we > don't copy page for this vma. Preparing anon_vma will be handled during > fault. > > Fixes: d2cd9ede6e19 ("mm,fork: introduce MADV_WIPEONFORK") > Signed-off-by: Li Xinhai > Cc: Rik van Riel > Cc: Kirill A. Shutemov > Cc: Matthew Wilcox Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov