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Thu, 25 Jan 2024 14:35:41 -0800 (PST) MIME-Version: 1.0 References: <20240122235208.work.748-kees@kernel.org> <20240123002814.1396804-55-keescook@chromium.org> In-Reply-To: <20240123002814.1396804-55-keescook@chromium.org> From: Andrey Konovalov Date: Thu, 25 Jan 2024 23:35:30 +0100 Message-ID: Subject: Re: [PATCH 55/82] kasan: Refactor intentional wrap-around test To: Kees Cook Cc: linux-hardening@vger.kernel.org, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , kasan-dev@googlegroups.com, linux-mm@kvack.org, "Gustavo A. R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 6F405C0003 X-Rspam-User: X-Stat-Signature: gx664tzrwq15kf9h794fy17836h9r33x X-Rspamd-Server: rspam03 X-HE-Tag: 1706222143-977447 X-HE-Meta: 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 WGJ9d8dz 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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: List-Subscribe: List-Unsubscribe: On Tue, Jan 23, 2024 at 1:29=E2=80=AFAM Kees Cook w= rote: > > In an effort to separate intentional arithmetic wrap-around from > unexpected wrap-around, we need to refactor places that depend on this > kind of math. One of the most common code patterns of this is: > > VAR + value < VAR > > Notably, this is considered "undefined behavior" for signed and pointer > types, which the kernel works around by using the -fno-strict-overflow > option in the build[1] (which used to just be -fwrapv). Regardless, we > want to get the kernel source to the position where we can meaningfully > instrument arithmetic wrap-around conditions and catch them when they > are unexpected, regardless of whether they are signed[2], unsigned[3], > or pointer[4] types. > > Refactor open-coded wrap-around addition test to use add_would_overflow()= . > This paves the way to enabling the wrap-around sanitizers in the future. > > Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f185365= 94 [1] > Link: https://github.com/KSPP/linux/issues/26 [2] > Link: https://github.com/KSPP/linux/issues/27 [3] > Link: https://github.com/KSPP/linux/issues/344 [4] > Cc: Andrey Ryabinin > Cc: Alexander Potapenko > Cc: Andrey Konovalov > Cc: Dmitry Vyukov > Cc: Vincenzo Frascino > Cc: Andrew Morton > Cc: kasan-dev@googlegroups.com > Cc: linux-mm@kvack.org > Signed-off-by: Kees Cook > --- > mm/kasan/generic.c | 2 +- > mm/kasan/sw_tags.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c > index df6627f62402..f9bc29ae09bd 100644 > --- a/mm/kasan/generic.c > +++ b/mm/kasan/generic.c > @@ -171,7 +171,7 @@ static __always_inline bool check_region_inline(const= void *addr, > if (unlikely(size =3D=3D 0)) > return true; > > - if (unlikely(addr + size < addr)) > + if (unlikely(add_would_overflow(addr, size))) > return !kasan_report(addr, size, write, ret_ip); > > if (unlikely(!addr_has_metadata(addr))) > diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c > index 220b5d4c6876..79a3bbd66c32 100644 > --- a/mm/kasan/sw_tags.c > +++ b/mm/kasan/sw_tags.c > @@ -80,7 +80,7 @@ bool kasan_check_range(const void *addr, size_t size, b= ool write, > if (unlikely(size =3D=3D 0)) > return true; > > - if (unlikely(addr + size < addr)) > + if (unlikely(add_would_overflow(addr, size))) > return !kasan_report(addr, size, write, ret_ip); > > tag =3D get_tag((const void *)addr); > -- > 2.34.1 > Acked-by: Andrey Konovalov Thanks!