Commit f171d695 authored by Mark Rutland's avatar Mark Rutland Committed by Kees Cook
Browse files

lkdtm/stackleak: check stack boundaries 



The stackleak code relies upon the current SP and lowest recorded SP
falling within expected task stack boundaries.

Check this at the start of the test.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Alexander Popov <alex.popov@linux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220427173128.2603085-12-mark.rutland@arm.com
parent f03a5093

drivers/misc/lkdtm/stackleak.c

+20 −0
Original line number Diff line number Diff line
@@ -35,6 +35,25 @@ static void noinstr check_stackleak_irqoff(void) 
	unsigned long poison_high, poison_low;

	bool test_failed = false;



	/*

	 * Check that the current and lowest recorded stack pointer values fall

	 * within the expected task stack boundaries. These tests should never

	 * fail unless the boundaries are incorrect or we're clobbering the

	 * STACK_END_MAGIC, and in either casee something is seriously wrong.

	 */

	if (current_sp < task_stack_low || current_sp >= task_stack_high) {

		pr_err("FAIL: current_stack_pointer (0x%lx) outside of task stack bounds [0x%lx..0x%lx]\n",

		       current_sp, task_stack_low, task_stack_high - 1);

		test_failed = true;

		goto out;

	}

	if (lowest_sp < task_stack_low || lowest_sp >= task_stack_high) {

		pr_err("FAIL: current->lowest_stack (0x%lx) outside of task stack bounds [0x%lx..0x%lx]\n",

		       lowest_sp, task_stack_low, task_stack_high - 1);

		test_failed = true;

		goto out;

	}



	/*

	 * Depending on what has run prior to this test, the lowest recorded

	 * stack pointer could be above or below the current stack pointer.
@@ -87,6 +106,7 @@ static void noinstr check_stackleak_irqoff(void) 
		poison_high - task_stack_low,

		task_stack_low - task_stack_base);



out:

	if (test_failed) {

		pr_err("FAIL: the thread stack is NOT properly erased!\n");

		pr_expected_config(CONFIG_GCC_PLUGIN_STACKLEAK);