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Mon, 28 Oct 2019 21:21:20 -0700 (PDT) Received: from localhost ([2001:44b8:802:1120:783a:2bb9:f7cb:7c3c]) by smtp.gmail.com with ESMTPSA id a5sm3908450pfk.172.2019.10.28.21.21.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Oct 2019 21:21:19 -0700 (PDT) From: Daniel Axtens To: kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org, aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, dvyukov@google.com, christophe.leroy@c-s.fr Cc: linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com, Daniel Axtens Subject: [PATCH v10 3/5] fork: support VMAP_STACK with KASAN_VMALLOC Date: Tue, 29 Oct 2019 15:20:57 +1100 Message-Id: <20191029042059.28541-4-dja@axtens.net> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191029042059.28541-1-dja@axtens.net> References: <20191029042059.28541-1-dja@axtens.net> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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: Supporting VMAP_STACK with KASAN_VMALLOC is straightforward: - clear the shadow region of vmapped stacks when swapping them in - tweak Kconfig to allow VMAP_STACK to be turned on with KASAN Reviewed-by: Dmitry Vyukov Signed-off-by: Daniel Axtens --- arch/Kconfig | 9 +++++---- kernel/fork.c | 4 ++++ 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 5f8a5d84dbbe..2d914990402f 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -843,16 +843,17 @@ config HAVE_ARCH_VMAP_STACK config VMAP_STACK default y bool "Use a virtually-mapped stack" - depends on HAVE_ARCH_VMAP_STACK && !KASAN + depends on HAVE_ARCH_VMAP_STACK + depends on !KASAN || KASAN_VMALLOC ---help--- Enable this if you want the use virtually-mapped kernel stacks with guard pages. This causes kernel stack overflows to be caught immediately rather than causing difficult-to-diagnose corruption. =20 - This is presently incompatible with KASAN because KASAN expects - the stack to map directly to the KASAN shadow map using a formula - that is incorrect if the stack is in vmalloc space. + To use this with KASAN, the architecture must support backing + virtual mappings with real shadow memory, and KASAN_VMALLOC must + be enabled. =20 config ARCH_OPTIONAL_KERNEL_RWX def_bool n diff --git a/kernel/fork.c b/kernel/fork.c index 954e875e72b1..a6e5249ad74b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -94,6 +94,7 @@ #include #include #include +#include =20 #include #include @@ -224,6 +225,9 @@ static unsigned long *alloc_thread_stack_node(struct = task_struct *tsk, int node) if (!s) continue; =20 + /* Clear the KASAN shadow of the stack. */ + kasan_unpoison_shadow(s->addr, THREAD_SIZE); + /* Clear stale pointers from reused stack. */ memset(s->addr, 0, THREAD_SIZE); =20 --=20 2.20.1