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stackleak: add on/off stack variants

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The stackleak_erase() code dynamically handles being on a task stack or
another stack. In most cases, this is a fixed property of the caller,
which the caller is aware of, as an architecture might always return
using the task stack, or might always return using a trampoline stack.

This patch adds stackleak_erase_on_task_stack() and
stackleak_erase_off_task_stack() functions which callers can use to
avoid on_thread_stack() check and associated redundant work when the
calling stack is known. The existing stackleak_erase() is retained as a
safe default.

There should be no functional change as a result of this patch.

Signed-off-by: Mark 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: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220427173128.2603085-13-mark.rutland@arm.com
This commit is contained in:
Mark Rutland 2022-04-27 18:31:27 +01:00 committed by Kees Cook
parent f171d695f3
commit 8111e67dee
1 changed files with 32 additions and 3 deletions
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35
kernel/stackleak.c
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@ -70,7 +70,7 @@ late_initcall(stackleak_sysctls_init);
#define skip_erasing() false
#endif /* CONFIG_STACKLEAK_RUNTIME_DISABLE */
static __always_inline void __stackleak_erase(void)
static __always_inline void __stackleak_erase(bool on_task_stack)
{
const unsigned long task_stack_low = stackleak_task_low_bound(current);
const unsigned long task_stack_high = stackleak_task_high_bound(current);
@ -96,7 +96,7 @@ static __always_inline void __stackleak_erase(void)
* function has a fixed-size stack frame, and the current stack pointer
* doesn't change while we write poison.
*/
if (on_thread_stack())
if (on_task_stack)
erase_high = current_stack_pointer;
else
erase_high = task_stack_high;
@ -110,12 +110,41 @@ static __always_inline void __stackleak_erase(void)
current->lowest_stack = task_stack_high;
}
/*
* Erase and poison the portion of the task stack used since the last erase.
* Can be called from the task stack or an entry stack when the task stack is
* no longer in use.
*/
asmlinkage void noinstr stackleak_erase(void)
{
if (skip_erasing())
return;
__stackleak_erase();
__stackleak_erase(on_thread_stack());
}
/*
* Erase and poison the portion of the task stack used since the last erase.
* Can only be called from the task stack.
*/
asmlinkage void noinstr stackleak_erase_on_task_stack(void)
{
if (skip_erasing())
return;
__stackleak_erase(true);
}
/*
* Erase and poison the portion of the task stack used since the last erase.
* Can only be called from a stack other than the task stack.
*/
asmlinkage void noinstr stackleak_erase_off_task_stack(void)
{
if (skip_erasing())
return;
__stackleak_erase(false);
}
void __used __no_caller_saved_registers noinstr stackleak_track_stack(void)