linux-kernel - [PATCH] kgdbts: fix hw_access_break

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-next>] [day] [month] [year] [list]

Message-ID: <20240812085459.291741-1-mail@florommel.de>
Date: Mon, 12 Aug 2024 10:54:59 +0200
From: Florian Rommel <mail@...rommel.de>
To: Jason Wessel <jason.wessel@...driver.com>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Douglas Anderson <dianders@...omium.org>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	kgdb-bugreport@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Cc: Florian Rommel <mail@...rommel.de>
Subject: [PATCH] kgdbts: fix hw_access_break_test

The test for access watchpoints (hw_access_break_test) was broken
(always failed) because the compiler optimized out the write to the
static helper variable (hw_break_val2), as it is never read anywhere.
This resulted in the target variable (hw_break_val) not being accessed
and thus the breakpoint not being triggered.

Remove the helper variable (hw_break_val2), and use READ_ONCE to force
reading the target variable (hw_break_val).

Signed-off-by: Florian Rommel <mail@...rommel.de>
---
 drivers/misc/kgdbts.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index 88b91ad8e541..0cf31164b470 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -95,6 +95,7 @@
 #include <linux/kallsyms.h>
 
 #include <asm/sections.h>
+#include <asm/rwonce.h>
 
 #define v1printk(a...) do {		\
 	if (verbose)			\
@@ -126,7 +127,6 @@ static int final_ack;
 static int force_hwbrks;
 static int hwbreaks_ok;
 static int hw_break_val;
-static int hw_break_val2;
 static int cont_instead_of_sstep;
 static unsigned long cont_thread_id;
 static unsigned long sstep_thread_id;
@@ -284,7 +284,7 @@ static void hw_rem_access_break(char *arg)
 
 static void hw_break_val_access(void)
 {
-	hw_break_val2 = hw_break_val;
+	READ_ONCE(hw_break_val);
 }
 
 static void hw_break_val_write(void)
-- 
2.46.0