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[59.167.251.205]) by smtp.gmail.com with ESMTPSA id p20sm75540475pgj.47.2019.07.24.22.55.22 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 24 Jul 2019 22:55:23 -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, dvyukov@google.com Cc: Daniel Axtens Subject: [PATCH 2/3] fork: support VMAP_STACK with KASAN_VMALLOC Date: Thu, 25 Jul 2019 15:55:02 +1000 Message-Id: <20190725055503.19507-3-dja@axtens.net> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190725055503.19507-1-dja@axtens.net> References: <20190725055503.19507-1-dja@axtens.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 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 a7b57dd42c26..e791196005e1 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -825,16 +825,17 @@ 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. - 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. config ARCH_OPTIONAL_KERNEL_RWX def_bool n diff --git a/kernel/fork.c b/kernel/fork.c index d8ae0f1b4148..ce3150fe8ff2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -94,6 +94,7 @@ #include #include #include +#include #include #include @@ -215,6 +216,9 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) if (!s) continue; + /* 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); -- 2.20.1