Commit 51fb34de authored by Andrey Konovalov's avatar Andrey Konovalov Committed by Linus Torvalds
Browse files

kasan, arm64: reset pointer tags of vmapped stacks 

Once tag-based KASAN modes start tagging vmalloc() allocations, kernel
stacks start getting tagged if CONFIG_VMAP_STACK is enabled.

Reset the tag of kernel stack pointers after allocation in
arch_alloc_vmap_stack().

For SW_TAGS KASAN, when CONFIG_KASAN_STACK is enabled, the instrumentation
can't handle the SP register being tagged.

For HW_TAGS KASAN, there's no instrumentation-related issues.  However,
the impact of having a tagged SP register needs to be properly evaluated,
so keep it non-tagged for now.

Note, that the memory for the stack allocation still gets tagged to catch
vmalloc-into-stack out-of-bounds accesses.

[andreyknvl@google.com: fix case when a stack is retrieved from cached_stacks]
  Link: https://lkml.kernel.org/r/f50c5f96ef896d7936192c888b0c0a7674e33184.1644943792.git.andreyknvl@google.com
[dan.carpenter@oracle.com: remove unnecessary check in alloc_thread_stack_node()]
  Link: https://lkml.kernel.org/r/20220301080706.GB17208@kili

Link: https://lkml.kernel.org/r/698c5ab21743c796d46c15d075b9481825973e34.1643047180.git.andreyknvl@google.com


Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarMarco Elver <elver@google.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c08e6a12

arch/arm64/include/asm/vmap_stack.h

+4 −1
Original line number Diff line number Diff line
@@ -17,10 +17,13 @@ 
 */

static inline unsigned long *arch_alloc_vmap_stack(size_t stack_size, int node)

{

	void *p;



	BUILD_BUG_ON(!IS_ENABLED(CONFIG_VMAP_STACK));



	return __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node,

	p = __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node,

			__builtin_return_address(0));

	return kasan_reset_tag(p);

}



#endif /* __ASM_VMAP_STACK_H */

kernel/fork.c

+6 −5
Original line number Diff line number Diff line
@@ -286,11 +286,13 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) 
		if (!s)

			continue;



		/* Mark stack accessible for KASAN. */

		/* Reset stack metadata. */

		kasan_unpoison_range(s->addr, THREAD_SIZE);



		stack = kasan_reset_tag(s->addr);



		/* Clear stale pointers from reused stack. */

		memset(s->addr, 0, THREAD_SIZE);

		memset(stack, 0, THREAD_SIZE);



		if (memcg_charge_kernel_stack(s)) {

			vfree(s->addr);
@@ -298,7 +300,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) 
		}



		tsk->stack_vm_area = s;

		tsk->stack = s->addr;

		tsk->stack = stack;

		return 0;

	}
@@ -326,7 +328,6 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) 
	 * so cache the vm_struct.

	 */

	tsk->stack_vm_area = vm;

	if (stack)

	stack = kasan_reset_tag(stack);

	tsk->stack = stack;

	return 0;