linux-kernel - [PATCH] microblaze: fix /dev/zero corruption from __clear

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: <1297361533-24627-1-git-send-email-steve@digidescorp.com>
Date:	Thu, 10 Feb 2011 12:12:13 -0600
From:	"Steven J. Magnani" <steve@...idescorp.com>
To:	microblaze-uclinux@...e.uq.edu.au
Cc:	monstr@...str.eu, linux-kernel@...r.kernel.org,
	"Steven J. Magnani" <steve@...idescorp.com>
Subject: [PATCH] microblaze: fix /dev/zero corruption from __clear_user()

A userland read of more than PAGE_SIZE bytes from /dev/zero results in
(a) not all of the bytes returned being zero, and
(b) memory corruption due to zeroing of bytes beyond the user buffer.

This is caused by improper constraints on the assembly __clear_user function.
The constrints don't indicate to the compiler that the pointer argument is
modified. Since the function is inline, this results in double-incrementing
of the pointer when __clear_user() is invoked through a multi-page read() of
/dev/zero. 

Signed-off-by: Steven J. Magnani <steve@...idescorp.com>
---
diff -uprN a/arch/microblaze/include/asm/uaccess.h b/arch/microblaze/include/asm/uaccess.h
--- a/arch/microblaze/include/asm/uaccess.h	2011-02-10 11:51:52.319226513 -0600
+++ b/arch/microblaze/include/asm/uaccess.h	2011-02-10 11:53:01.064857179 -0600
@@ -120,16 +120,16 @@ static inline unsigned long __must_check
 {
 	/* normal memset with two words to __ex_table */
 	__asm__ __volatile__ (				\
-			"1:	sb	r0, %2, r0;"	\
+			"1:	sb	r0, %1, r0;"	\
 			"	addik	%0, %0, -1;"	\
 			"	bneid	%0, 1b;"	\
-			"	addik	%2, %2, 1;"	\
+			"	addik	%1, %1, 1;"	\
 			"2:			"	\
 			__EX_TABLE_SECTION		\
 			".word	1b,2b;"			\
 			".previous;"			\
-		: "=r"(n)				\
-		: "0"(n), "r"(to)
+		: "=r"(n), "=r"(to)			\
+		: "0"(n), "1"(to)
 	);
 	return n;
 }

--
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/