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bh=8nCh8U5O/ZXKVmZDEcs6WxwzpGVNHClVBgr7qeBYLZo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=AbMZvzyFq3YIQxOLWlCrcVKKv2q9ooVq+0R/X8C13HjYid7pOqd9s8B7t9MCgSMEn 2cfntWoQB1s4un4Dep+dzyBa0rfVFTIIAVYRMA76AavkmjoCSnXr55dxbOZvT8nlSF +kMpR90gnarYX+OKvSW/5j8V2T5BonVUh7g57JTQ= Date: Thu, 2 Mar 2023 17:57:34 -0800 From: Andrew Morton To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport , Andrea Arcangeli , Peter Xu , Jerome Glisse , Shaohua Li Subject: Re: [PATCH v1] mm/userfaultfd: propagate uffd-wp bit when PTE-mapping the huge zeropage Message-Id: <20230302175734.7be9da18e4724720a12a4b40@linux-foundation.org> In-Reply-To: <20230302175423.589164-1-david@redhat.com> References: <20230302175423.589164-1-david@redhat.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 083741C0009 X-Stat-Signature: nrcunnsuoo4dtmtifomw3z5w9bkmcxe1 X-Rspam-User: X-HE-Tag: 1677808657-910221 X-HE-Meta: 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 iDNGhA5B 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 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 Thu, 2 Mar 2023 18:54:23 +0100 David Hildenbrand wrote: > Currently, we'd lose the userfaultfd-wp marker when PTE-mapping a huge > zeropage, resulting in the next write faults in the PMD range > not triggering uffd-wp events. > > Various actions (partial MADV_DONTNEED, partial mremap, partial munmap, > partial mprotect) could trigger this. However, most importantly, > un-protecting a single sub-page from the userfaultfd-wp handler when > processing a uffd-wp event will PTE-map the shared huge zeropage and > lose the uffd-wp bit for the remainder of the PMD. > > Let's properly propagate the uffd-wp bit to the PMDs. > > ... > > Fixes: e06f1e1dd499 ("userfaultfd: wp: enabled write protection in userfaultfd API") > Cc: Andrew Morton > Cc: Mike Rapoport > Cc: Andrea Arcangeli > Cc: Peter Xu > Cc: Jerome Glisse > Cc: Shaohua Li > Signed-off-by: David Hildenbrand Do you agree that a -stable backport is appropriate?