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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b23sm22104993pfi.135.2021.10.06.15.07.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Oct 2021 15:07:40 -0700 (PDT) Date: Wed, 6 Oct 2021 15:07:40 -0700 From: Kees Cook To: Matthew Wilcox Cc: linux-mm@kvack.org, Thomas Gleixner Subject: Re: [PATCH v2 3/3] mm/usercopy: Detect compound page overruns Message-ID: <202110061506.CF5BDD0@keescook> References: <20211006124226.209484-1-willy@infradead.org> <20211006124226.209484-4-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=KOnxafq+; spf=pass (imf27.hostedemail.com: domain of keescook@chromium.org designates 209.85.216.43 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 43EB67001F45 X-Stat-Signature: kp17q4khr3he8qhh3wfgsft9d9ewjz6q X-HE-Tag: 1633558062-59857 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 Wed, Oct 06, 2021 at 03:08:46PM +0100, Matthew Wilcox wrote: > On Wed, Oct 06, 2021 at 01:42:26PM +0100, Matthew Wilcox (Oracle) wrote: > > Move the compound page overrun detection out of > > CONFIG_HARDENED_USERCOPY_PAGESPAN so it's enabled for more people. > > > > Signed-off-by: Matthew Wilcox (Oracle) > > Acked-by: Kees Cook > > --- > > mm/usercopy.c | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/mm/usercopy.c b/mm/usercopy.c > > index 63476e1506e0..b825c4344917 100644 > > --- a/mm/usercopy.c > > +++ b/mm/usercopy.c > > @@ -194,11 +194,6 @@ static inline void check_page_span(const void *ptr, unsigned long n, > > ((unsigned long)end & (unsigned long)PAGE_MASK))) > > return; > > > > - /* Allow if fully inside the same compound (__GFP_COMP) page. */ > > - endpage = virt_to_head_page(end); > > - if (likely(endpage == page)) > > - return; > > - > > /* > > * Reject if range is entirely either Reserved (i.e. special or > > * device memory), or CMA. Otherwise, reject since the object spans > > Needs an extra hunk to avoid a warning with that config: Ah yeah, good catch. > > @@ -163,7 +163,6 @@ static inline void check_page_span(const void *ptr, unsigned long n, > { > #ifdef CONFIG_HARDENED_USERCOPY_PAGESPAN > const void *end = ptr + n - 1; > - struct page *endpage; > bool is_reserved, is_cma; > > /* > > I'll wait a few days and send a v3. When you send v3, can you CC linux-hardening@vger.kernel.org too? Thanks for poking at this! -Kees -- Kees Cook