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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id q91sm3157033pjb.11.2020.04.02.00.52.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2020 00:52:43 -0700 (PDT) Date: Thu, 2 Apr 2020 00:52:41 -0700 From: Kees Cook To: Christophe Leroy Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , airlied@linux.ie, daniel@ffwll.ch, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, hpa@zytor.com, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-arch@vger.kernel.org Subject: Re: [PATCH RESEND 4/4] powerpc/uaccess: Implement user_read_access_begin and user_write_access_begin Message-ID: <202004020052.47DB88E3C@keescook> References: <27106d62fdbd4ffb47796236050e418131cb837f.1585811416.git.christophe.leroy@c-s.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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, Apr 02, 2020 at 07:34:19AM +0000, Christophe Leroy wrote: > Add support for selective read or write user access with > user_read_access_begin/end and user_write_access_begin/end. > > Signed-off-by: Christophe Leroy Reviewed-by: Kees Cook -Kees > --- > arch/powerpc/include/asm/book3s/32/kup.h | 4 ++-- > arch/powerpc/include/asm/kup.h | 14 +++++++++++++- > arch/powerpc/include/asm/uaccess.h | 22 ++++++++++++++++++++++ > 3 files changed, 37 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h > index 3c0ba22dc360..1617e73bee30 100644 > --- a/arch/powerpc/include/asm/book3s/32/kup.h > +++ b/arch/powerpc/include/asm/book3s/32/kup.h > @@ -108,7 +108,7 @@ static __always_inline void allow_user_access(void __user *to, const void __user > u32 addr, end; > > BUILD_BUG_ON(!__builtin_constant_p(dir)); > - BUILD_BUG_ON(dir == KUAP_CURRENT); > + BUILD_BUG_ON(dir & ~KUAP_READ_WRITE); > > if (!(dir & KUAP_WRITE)) > return; > @@ -131,7 +131,7 @@ static __always_inline void prevent_user_access(void __user *to, const void __us > > BUILD_BUG_ON(!__builtin_constant_p(dir)); > > - if (dir == KUAP_CURRENT) { > + if (dir & KUAP_CURRENT_WRITE) { > u32 kuap = current->thread.kuap; > > if (unlikely(!kuap)) > diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h > index 92bcd1a26d73..c745ee41ad66 100644 > --- a/arch/powerpc/include/asm/kup.h > +++ b/arch/powerpc/include/asm/kup.h > @@ -10,7 +10,9 @@ > * Use the current saved situation instead of the to/from/size params. > * Used on book3s/32 > */ > -#define KUAP_CURRENT 4 > +#define KUAP_CURRENT_READ 4 > +#define KUAP_CURRENT_WRITE 8 > +#define KUAP_CURRENT (KUAP_CURRENT_READ | KUAP_CURRENT_WRITE) > > #ifdef CONFIG_PPC64 > #include > @@ -101,6 +103,16 @@ static inline void prevent_current_access_user(void) > prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT); > } > > +static inline void prevent_current_read_from_user(void) > +{ > + prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT_READ); > +} > + > +static inline void prevent_current_write_to_user(void) > +{ > + prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT_WRITE); > +} > + > #endif /* !__ASSEMBLY__ */ > > #endif /* _ASM_POWERPC_KUAP_H_ */ > diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h > index 2f500debae21..4427d419eb1d 100644 > --- a/arch/powerpc/include/asm/uaccess.h > +++ b/arch/powerpc/include/asm/uaccess.h > @@ -468,6 +468,28 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t > #define user_access_save prevent_user_access_return > #define user_access_restore restore_user_access > > +static __must_check inline bool > +user_read_access_begin(const void __user *ptr, size_t len) > +{ > + if (unlikely(!access_ok(ptr, len))) > + return false; > + allow_read_from_user(ptr, len); > + return true; > +} > +#define user_read_access_begin user_read_access_begin > +#define user_read_access_end prevent_current_read_from_user > + > +static __must_check inline bool > +user_write_access_begin(const void __user *ptr, size_t len) > +{ > + if (unlikely(!access_ok(ptr, len))) > + return false; > + allow_write_to_user((void __user *)ptr, len); > + return true; > +} > +#define user_write_access_begin user_write_access_begin > +#define user_write_access_end prevent_current_write_to_user > + > #define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0) > #define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e) > #define unsafe_put_user(x, p, e) unsafe_op_wrap(__put_user_allowed(x, p), e) > -- > 2.25.0 > -- Kees Cook