linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
	Alexander Potapenko <glider@google.com>,
	Joe Perches <joe@perches.com>, Andy Whitcroft <apw@canonical.com>,
	x86@kernel.org, drbd-dev@lists.linbit.com,
	linux-block@vger.kernel.org, b43-dev@lists.infradead.org,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	linux-ide@vger.kernel.org, linux-clk@vger.kernel.org,
	linux-spi@vger.kernel.org, linux-mm@kvack.org,
	clang-built-linux@googlegroups.com
Subject: [PATCH 01/10] x86/mm/numa: Remove uninitialized_var() usage
Date: Wed,  3 Jun 2020 16:31:54 -0700	[thread overview]
Message-ID: <20200603233203.1695403-2-keescook@chromium.org> (raw)
In-Reply-To: <20200603233203.1695403-1-keescook@chromium.org>

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings (e.g.
"unused variable"). If the compiler thinks it is uninitialized, either
simply initialize the variable or make compiler changes. As a precursor
to removing[2] this[3] macro[4], refactor code to avoid its need.

The original reason for its use here was to work around the #ifdef
being the only place the variable was used. This is better expressed
using IS_ENABLED() and a new code block where the variable can be used
unconditionally.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/mm/numa.c                | 18 +++++++++---------
 include/linux/page-flags-layout.h |  2 +-
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 59ba008504dc..38eeb15f3b07 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -541,7 +541,6 @@ static void __init numa_clear_kernel_node_hotplug(void)
 
 static int __init numa_register_memblks(struct numa_meminfo *mi)
 {
-	unsigned long uninitialized_var(pfn_align);
 	int i, nid;
 
 	/* Account for nodes with cpus and no memory */
@@ -569,15 +568,16 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
 	 * If sections array is gonna be used for pfn -> nid mapping, check
 	 * whether its granularity is fine enough.
 	 */
-#ifdef NODE_NOT_IN_PAGE_FLAGS
-	pfn_align = node_map_pfn_alignment();
-	if (pfn_align && pfn_align < PAGES_PER_SECTION) {
-		printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
-		       PFN_PHYS(pfn_align) >> 20,
-		       PFN_PHYS(PAGES_PER_SECTION) >> 20);
-		return -EINVAL;
+	if (IS_ENABLED(NODE_NOT_IN_PAGE_FLAGS)) {
+		unsigned long pfn_align = node_map_pfn_alignment();
+
+		if (pfn_align && pfn_align < PAGES_PER_SECTION) {
+			pr_warn("Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
+				PFN_PHYS(pfn_align) >> 20,
+				PFN_PHYS(PAGES_PER_SECTION) >> 20);
+			return -EINVAL;
+		}
 	}
-#endif
 	if (!numa_meminfo_cover_memory(mi))
 		return -EINVAL;
 
diff --git a/include/linux/page-flags-layout.h b/include/linux/page-flags-layout.h
index 71283739ffd2..1a4cdec2bd29 100644
--- a/include/linux/page-flags-layout.h
+++ b/include/linux/page-flags-layout.h
@@ -100,7 +100,7 @@
  * there.  This includes the case where there is no node, so it is implicit.
  */
 #if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
-#define NODE_NOT_IN_PAGE_FLAGS
+#define NODE_NOT_IN_PAGE_FLAGS 1
 #endif
 
 #if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
-- 
2.25.1


  reply	other threads:[~2020-06-03 23:34 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-03 23:31 [PATCH 00/10] Remove uninitialized_var() macro Kees Cook
2020-06-03 23:31 ` Kees Cook [this message]
2020-06-04  7:58   ` [PATCH 01/10] x86/mm/numa: Remove uninitialized_var() usage Thomas Gleixner
2020-06-04 11:41     ` Miguel Ojeda
2020-06-04 14:56       ` Kees Cook
2020-06-04 15:22         ` Miguel Ojeda
2020-06-04 14:34     ` Kees Cook
2020-06-04 21:39       ` Thomas Gleixner
2020-06-04 22:39         ` Kees Cook
2020-06-03 23:31 ` [PATCH 02/10] drbd: " Kees Cook
2020-06-04 19:56   ` Nick Desaulniers
2020-06-03 23:31 ` [PATCH 03/10] b43: " Kees Cook
2020-06-04 20:08   ` Nick Desaulniers
2020-06-04 20:18     ` Kees Cook
2020-06-04 20:25       ` Nick Desaulniers
2020-06-05  9:20   ` Kalle Valo
2020-06-03 23:31 ` [PATCH 04/10] rtlwifi: rtl8192cu: " Kees Cook
2020-06-04 20:16   ` Nick Desaulniers
2020-06-05  9:18   ` Kalle Valo
2020-06-03 23:31 ` [PATCH 05/10] ide: " Kees Cook
2020-06-04 19:29   ` Nick Desaulniers
2020-06-04 20:20     ` Kees Cook
2020-06-04 20:29       ` Nick Desaulniers
2020-06-15 19:32         ` Kees Cook
2020-06-04 20:58       ` Sedat Dilek
2020-06-03 23:31 ` [PATCH 06/10] clk: st: " Kees Cook
2020-06-04  4:38   ` Stephen Boyd
2020-06-03 23:32 ` [PATCH 07/10] spi: davinci: " Kees Cook
2020-06-04 19:40   ` Nick Desaulniers
2020-06-03 23:32 ` [PATCH 08/10] checkpatch: Remove awareness of uninitialized_var() macro Kees Cook
2020-06-04  0:02   ` Joe Perches
2020-06-04  1:40     ` Kees Cook
2020-06-04  1:47       ` Joe Perches
2020-06-04  2:44         ` Kees Cook
2020-06-04  2:53           ` Sedat Dilek
2020-06-04  3:46             ` Kees Cook
2020-06-03 23:32 ` [PATCH 09/10] treewide: Remove uninitialized_var() usage Kees Cook
2020-06-04  3:33   ` Nathan Chancellor
2020-06-04  4:02     ` Kees Cook
2020-06-04 10:45   ` Leon Romanovsky
2020-06-04 13:23   ` Jason Gunthorpe
2020-06-04 14:59     ` Kees Cook
2020-06-04 17:57       ` Jason Gunthorpe
2020-06-04 19:09       ` Geert Uytterhoeven
2020-06-05  9:25   ` Kalle Valo
2020-06-03 23:32 ` [PATCH 10/10] compiler: Remove uninitialized_var() macro Kees Cook
2020-06-04  0:00   ` Bart Van Assche
2020-06-04  0:50   ` Miguel Ojeda
2020-06-04  1:23 ` [PATCH 00/10] " Sedat Dilek
2020-06-04  1:44   ` Kees Cook
2020-06-04  1:46     ` Sedat Dilek
2020-06-04  3:33 ` Nathan Chancellor
2020-06-04  7:26   ` Sedat Dilek
2020-06-04 14:27     ` 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=20200603233203.1695403-2-keescook@chromium.org \
    --to=keescook@chromium.org \
    --cc=apw@canonical.com \
    --cc=b43-dev@lists.infradead.org \
    --cc=clang-built-linux@googlegroups.com \
    --cc=drbd-dev@lists.linbit.com \
    --cc=glider@google.com \
    --cc=joe@perches.com \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-clk@vger.kernel.org \
    --cc=linux-ide@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-spi@vger.kernel.org \
    --cc=linux-wireless@vger.kernel.org \
    --cc=miguel.ojeda.sandonis@gmail.com \
    --cc=netdev@vger.kernel.org \
    --cc=torvalds@linux-foundation.org \
    --cc=x86@kernel.org \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body.
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).