arm64: Use larger stacks when KASAN is selected

AddressSanitizer instrumentation can significantly bloat the stack, and
with GCC 7 this can result in stack overflows at boot time in some
configurations.

We can avoid this by doubling our stack size when KASAN is in use, as is
already done on x86 (and has been since KASAN was introduced).
Regardless of other patches to decrease KASAN's stack utilization,
kernels built with KASAN will always require more stack space than those
built without, and we should take this into account.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit b02faed15d86f846b0f23f47b92e0782baa873ed)

CVE-2017-5753
CVE-2017-5715
CVE-2017-5754

Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 3585a5e2615105162f82510f64917b094974a2a4..f7c4d2146aed09b715a59506f7e01ab0d167f3de 100644 (file)
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -95,16 +95,19 @@
 #define KERNEL_END        _end
 
 /*
- * The size of the KASAN shadow region. This should be 1/8th of the
- * size of the entire kernel virtual address space.
+ * KASAN requires 1/8th of the kernel virtual address space for the shadow
+ * region. KASAN can bloat the stack significantly, so double the (minimum)
+ * stack size when KASAN is in use.
  */
 #ifdef CONFIG_KASAN
 #define KASAN_SHADOW_SIZE      (UL(1) << (VA_BITS - 3))
+#define KASAN_THREAD_SHIFT     1
 #else
 #define KASAN_SHADOW_SIZE      (0)
+#define KASAN_THREAD_SHIFT     0
 #endif
 
-#define MIN_THREAD_SHIFT       14
+#define MIN_THREAD_SHIFT       (14 + KASAN_THREAD_SHIFT)
 
 /*
  * VMAP'd stacks are allocated at page granularity, so we must ensure that such