stackleak: remove redundant check

In __stackleak_erase() we check that the `erase_low` value derived from
`current->lowest_stack` is above the lowest legitimate stack pointer
value, but this is already enforced by stackleak_track_stack() when
recording the lowest stack value.

Remove the redundant check.

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/20220427173128.2603085-4-mark.rutland@arm.com

diff --git a/kernel/stackleak.c b/kernel/stackleak.c
index 753eab797a04dc9f017ebcca40c03f14b8c6bb62..f7a0f8cf73c37d8b50e739445411402f65abf1d0 100644 (file)
--- a/kernel/stackleak.c
+++ b/kernel/stackleak.c
@@ -78,10 +78,6 @@ static __always_inline void __stackleak_erase(void)
        unsigned int poison_count = 0;
        const unsigned int depth = STACKLEAK_SEARCH_DEPTH / sizeof(unsigned long);
 
-       /* Check that 'lowest_stack' value is sane */
-       if (unlikely(kstack_ptr - boundary >= THREAD_SIZE))
-               kstack_ptr = boundary;
-
        /* Search for the poison value in the kernel stack */
        while (kstack_ptr > boundary && poison_count <= depth) {
                if (*(unsigned long *)kstack_ptr == STACKLEAK_POISON)