LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Kees Cook <keescook@chromium.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] lkdtm/heap: Avoid __alloc_size hint warning
Date: Tue, 17 Aug 2021 21:45:40 -0700	[thread overview]
Message-ID: <20210818044540.1601664-1-keescook@chromium.org> (raw)

Once __alloc_size hints have been added, the compiler will
(correctly!) see this as an overflow. We are, however, trying to test
for this condition, so work around it with a volatile int.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/misc/lkdtm/heap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 3d9aae5821a0..e59fcbe00ae0 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -12,6 +12,8 @@ static struct kmem_cache *double_free_cache;
 static struct kmem_cache *a_cache;
 static struct kmem_cache *b_cache;
 
+static volatile int __offset = 1;
+
 /*
  * If there aren't guard pages, it's likely that a consecutive allocation will
  * let us overflow into the second allocation without overwriting something real.
@@ -24,7 +26,7 @@ void lkdtm_VMALLOC_LINEAR_OVERFLOW(void)
 	two = vzalloc(PAGE_SIZE);
 
 	pr_info("Attempting vmalloc linear overflow ...\n");
-	memset(one, 0xAA, PAGE_SIZE + 1);
+	memset(one, 0xAA, PAGE_SIZE + __offset);
 
 	vfree(two);
 	vfree(one);
-- 
2.30.2


             reply	other threads:[~2021-08-18  4:45 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18  4:45 Kees Cook [this message]
2021-08-18 14:01 ` Greg Kroah-Hartman
2021-08-18 17:32   ` Kees Cook

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210818044540.1601664-1-keescook@chromium.org \
    --to=keescook@chromium.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --subject='Re: [PATCH] lkdtm/heap: Avoid __alloc_size hint warning' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).