linux-kernel - [PATCH V2] omap2/omapfb: make DBG() more resistant in if-else constructions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1305025653-17138-1-git-send-email-ndevos@redhat.com>
Date:	Tue, 10 May 2011 12:07:33 +0100
From:	Niels de Vos <ndevos@...hat.com>
To:	linux-omap@...r.kernel.org
Cc:	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Sanjeev Premi <premi@...com>, Niels de Vos <ndevos@...hat.com>
Subject: [PATCH V2] omap2/omapfb: make DBG() more resistant in if-else constructions

When DBG() is used in a simple if-else, the resulting code path
currently depends on the definition of DBG(). Inserting the statement in
a "do { ... } while (0)" prevents this possible misuse.

Signed-off-by: Niels de Vos <ndevos@...hat.com>

---
V2: add the missing closing }

Note, I have not found any offenders, but a mistake can easily be made.
The following example shows what can go wrong if little intention is
paid to the definition of the DBG() macro.

Example:
	if something_went_wrong()
		DBG("oh no, something went wrong!\n");
	else
		printk("all went fine\n");

Old result where the else is placed inside the first if-statment:
	if something_went_wrong() {
		if (omapfb_debug) {
			printk(KERN_DEBUG "oh no, something went wrong!\n");
		} else {
			printk("all went fine\n");
		}
	}

New result where the else is an alternative to the first if-statement:
	if something_went_wrong() {
		do {
			if (omapfb_debug)
				printk(KERN_DEBUG "oh no, something went wrong!\n");
		} while (0);
	} else {
		printk("all went fine\n");
	}
---
 drivers/video/omap2/omapfb/omapfb.h |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/video/omap2/omapfb/omapfb.h b/drivers/video/omap2/omapfb/omapfb.h
index 1305fc9..456c586 100644
--- a/drivers/video/omap2/omapfb/omapfb.h
+++ b/drivers/video/omap2/omapfb/omapfb.h
@@ -34,8 +34,10 @@
 #ifdef DEBUG
 extern unsigned int omapfb_debug;
 #define DBG(format, ...) \
-	if (omapfb_debug) \
-		printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__)
+	do { \
+		if (omapfb_debug) \
+			printk(KERN_DEBUG "OMAPFB: " format, ## __VA_ARGS__); \
+	} while (0)
 #else
 #define DBG(format, ...)
 #endif
-- 
1.7.4.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/