From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vincenzo Frascino Subject: Re: [PATCH v17 02/15] lib, arm64: untag user pointers in strn*_user Date: Wed, 12 Jun 2019 15:28:15 +0100 Message-ID: <0bbc5f4f-9812-463c-48c1-4929bef801da@arm.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Andrey Konovalov , 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 Cc: Catalin Marinas , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Kees Cook , 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 List-Id: linux-rdma@vger.kernel.org On 12/06/2019 12:43, 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: Khalid Aziz > Acked-by: Kees Cook > Reviewed-by: Catalin Marinas > Signed-off-by: Andrey Konovalov Reviewed-by: Vincenzo Frascino > --- > 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; > -- Regards, Vincenzo