From: Mark Rutland Date: Wed, 27 Apr 2022 17:31:23 +0000 (+0100) Subject: lkdtm/stackleak: avoid spurious failure X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4130a61cebb1843517d68017a967f27fb602b885;p=linux.git lkdtm/stackleak: avoid spurious failure The lkdtm_STACKLEAK_ERASING() test scans for a contiguous block of poison values between the low stack bound and the stack pointer, and fails if it does not find a sufficiently large block. This can happen legitimately if the scan the low stack bound, which could occur if functions called prior to lkdtm_STACKLEAK_ERASING() used a large amount of stack. If this were to occur, it means that the erased portion of the stack is smaller than the size used by the scan, but does not cause a functional problem In practice this is unlikely to happen, but as this is legitimate and would not result in a functional problem, the test should not fail in this case. Remove the spurious failure case. Signed-off-by: Mark Rutland Cc: Alexander Popov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220427173128.2603085-9-mark.rutland@arm.com --- diff --git a/drivers/misc/lkdtm/stackleak.c b/drivers/misc/lkdtm/stackleak.c index 00db21ff115e4..707d530d509b7 100644 --- a/drivers/misc/lkdtm/stackleak.c +++ b/drivers/misc/lkdtm/stackleak.c @@ -53,13 +53,6 @@ void lkdtm_STACKLEAK_ERASING(void) found = 0; } - if (found <= check_depth) { - pr_err("FAIL: the erased part is not found (checked %lu bytes)\n", - i * sizeof(unsigned long)); - test_failed = true; - goto end; - } - pr_info("the erased part begins after %lu not poisoned bytes\n", (i - found) * sizeof(unsigned long));