Commit 48ac3c18 authored Jul 14, 2017 by Mark Rutland

fork: allow arch-override of VMAP stack alignment



In some cases, an architecture might wish its stacks to be aligned to a
boundary larger than THREAD_SIZE. For example, using an alignment of
double THREAD_SIZE can allow for stack overflows smaller than
THREAD_SIZE to be detected by checking a single bit of the stack
pointer.

This patch allows architectures to override the alignment of VMAP'd
stacks, by defining THREAD_ALIGN. Where not defined, this defaults to
THREAD_SIZE, as is the case today.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: linux-kernel@vger.kernel.org

parent c5bc503c

include/linux/thread_info.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -38,6 +38,10 @@ enum {

		#ifdef __KERNEL__

		#ifndef THREAD_ALIGN
		#define THREAD_ALIGN THREAD_SIZE
		#endif

		#ifdef CONFIG_DEBUG_STACK_USAGE
		# define THREADINFO_GFP (GFP_KERNEL_ACCOUNT \| __GFP_NOTRACK \| \
		__GFP_ZERO)

kernel/fork.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -88,6 +88,7 @@
		#include <linux/sysctl.h>
		#include <linux/kcov.h>
		#include <linux/livepatch.h>
		#include <linux/thread_info.h>

		#include <asm/pgtable.h>
		#include <asm/pgalloc.h>
		@@ -217,7 +218,7 @@ static unsigned long alloc_thread_stack_node(struct task_struct tsk, int node)
		return s->addr;
		}

		stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
		stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
		VMALLOC_START, VMALLOC_END,
		THREADINFO_GFP,
		PAGE_KERNEL,

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