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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id l13sm3156889pjq.20.2019.06.07.20.48.08 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 07 Jun 2019 20:48:08 -0700 (PDT) Date: Fri, 7 Jun 2019 20:48:07 -0700 From: Kees Cook To: Andrey Konovalov Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Catalin Marinas , Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Luc Van Oostenryck , Dave Martin , Khalid Aziz , enh , Jason Gunthorpe , Christoph Hellwig , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Kevin Brodsky , Szabolcs Nagy Subject: Re: [PATCH v16 03/16] lib, arm64: untag user pointers in strn*_user Message-ID: <201906072047.50371DBE2@keescook> References: <14f17ef1902aa4f07a39f96879394e718a1f5dc1.1559580831.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14f17ef1902aa4f07a39f96879394e718a1f5dc1.1559580831.git.andreyknvl@google.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jun 03, 2019 at 06:55:05PM +0200, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > strncpy_from_user and strnlen_user accept user addresses as arguments, and > do not go through the same path as copy_from_user and others, so here we > need to handle the case of tagged user addresses separately. > > Untag user pointers passed to these functions. > > Note, that this patch only temporarily untags the pointers to perform > validity checks, but then uses them as is to perform user memory accesses. > > Reviewed-by: Catalin Marinas > Signed-off-by: Andrey Konovalov Acked-by: Kees Cook -Kees > --- > lib/strncpy_from_user.c | 3 ++- > lib/strnlen_user.c | 3 ++- > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c > index 023ba9f3b99f..dccb95af6003 100644 > --- a/lib/strncpy_from_user.c > +++ b/lib/strncpy_from_user.c > @@ -6,6 +6,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -108,7 +109,7 @@ long strncpy_from_user(char *dst, const char __user *src, long count) > return 0; > > max_addr = user_addr_max(); > - src_addr = (unsigned long)src; > + src_addr = (unsigned long)untagged_addr(src); > if (likely(src_addr < max_addr)) { > unsigned long max = max_addr - src_addr; > long retval; > diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c > index 7f2db3fe311f..28ff554a1be8 100644 > --- a/lib/strnlen_user.c > +++ b/lib/strnlen_user.c > @@ -2,6 +2,7 @@ > #include > #include > #include > +#include > > #include > > @@ -109,7 +110,7 @@ long strnlen_user(const char __user *str, long count) > return 0; > > max_addr = user_addr_max(); > - src_addr = (unsigned long)str; > + src_addr = (unsigned long)untagged_addr(str); > if (likely(src_addr < max_addr)) { > unsigned long max = max_addr - src_addr; > long retval; > -- > 2.22.0.rc1.311.g5d7573a151-goog > -- Kees Cook