diff options
author | Mark Rutland <mark.rutland@arm.com> | 2022-04-27 18:31:25 +0100 |
---|---|---|
committer | Kees Cook <keescook@chromium.org> | 2022-05-08 01:33:08 -0700 |
commit | f03a50938decaa601f02294e4d057fb0048ca9ca (patch) | |
tree | ab423d6a439df190bc88905c336210f424b5cc46 | |
parent | 72b61896f2b47fa4b98e86184bc0e6ddbd1a8db1 (diff) | |
download | linux-stable-f03a50938decaa601f02294e4d057fb0048ca9ca.tar.gz linux-stable-f03a50938decaa601f02294e4d057fb0048ca9ca.tar.bz2 linux-stable-f03a50938decaa601f02294e4d057fb0048ca9ca.zip |
lkdtm/stackleak: prevent unexpected stack usage
The lkdtm_STACKLEAK_ERASING() test is instrumentable and runs with IRQs
unmasked, so it's possible for unrelated code to clobber the task stack
and/or manipulate current->lowest_stack while the test is running,
resulting in spurious failures.
The regular stackleak erasing code is non-instrumentable and runs with
IRQs masked, preventing similar issues.
Make the body of the test non-instrumentable, and run it with IRQs
masked, avoiding such spurious failures.
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: Catalin Marinas <catalin.marinas@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220427173128.2603085-11-mark.rutland@arm.com
-rw-r--r-- | drivers/misc/lkdtm/stackleak.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/drivers/misc/lkdtm/stackleak.c b/drivers/misc/lkdtm/stackleak.c index 0aafa46ced7d..46c60761a05e 100644 --- a/drivers/misc/lkdtm/stackleak.c +++ b/drivers/misc/lkdtm/stackleak.c @@ -11,7 +11,20 @@ #include "lkdtm.h" #include <linux/stackleak.h> -void lkdtm_STACKLEAK_ERASING(void) +/* + * Check that stackleak tracks the lowest stack pointer and erases the stack + * below this as expected. + * + * To prevent the lowest stack pointer changing during the test, IRQs are + * masked and instrumentation of this function is disabled. We assume that the + * compiler will create a fixed-size stack frame for this function. + * + * Any non-inlined function may make further use of the stack, altering the + * lowest stack pointer and/or clobbering poison values. To avoid spurious + * failures we must avoid printing until the end of the test or have already + * encountered a failure condition. + */ +static void noinstr check_stackleak_irqoff(void) { const unsigned long task_stack_base = (unsigned long)task_stack_page(current); const unsigned long task_stack_low = stackleak_task_low_bound(current); @@ -81,3 +94,12 @@ void lkdtm_STACKLEAK_ERASING(void) pr_info("OK: the rest of the thread stack is properly erased\n"); } } + +void lkdtm_STACKLEAK_ERASING(void) +{ + unsigned long flags; + + local_irq_save(flags); + check_stackleak_irqoff(); + local_irq_restore(flags); +} |