linux-kernel - [PATCH 2/4] ARC: Fix 32-bit wrap around in access

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Date:	Fri, 27 Sep 2013 16:27:35 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	<linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>
CC:	<arc-linux-dev@...opsys.com>, <u.kleine-koenig@...gutronix.de>,
	Noam Camus <noamc@...hip.com>,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [PATCH 2/4] ARC: Fix 32-bit wrap around in access_ok()

Anton reported

 | LTP tests syscalls/process_vm_readv01 and process_vm_writev01 fail
 | similarly in one testcase test_iov_invalid -> lvec->iov_base.
 | Testcase expects errno EFAULT and return code -1,
 | but it gets return code 1 and ERRNO is 0 what means success.

Essentially test case was passing a pointer of -1 which access_ok()
was not catching. It was doing [@addr + @sz <= TASK_SIZE] which would
pass for @addr == -1

Fixed that by rewriting as [@addr <= TASK_SIZE - @sz]

Reported-by: Anton Kolesov <Anton.Kolesov@...opsys.com>
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/arc/include/asm/uaccess.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 3242082..30c9baf 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -43,7 +43,7 @@
  * Because it essentially checks if buffer end is within limit and @len is
  * non-ngeative, which implies that buffer start will be within limit too.
  *
- * The reason for rewriting being, for majorit yof cases, @len is generally
+ * The reason for rewriting being, for majority of cases, @len is generally
  * compile time constant, causing first sub-expression to be compile time
  * subsumed.
  *
@@ -53,7 +53,7 @@
  *
  */
 #define __user_ok(addr, sz)	(((sz) <= TASK_SIZE) && \
-				 (((addr)+(sz)) <= get_fs()))
+				 ((addr) <= (get_fs() - (sz))))
 #define __access_ok(addr, sz)	(unlikely(__kernel_ok) || \
 				 likely(__user_ok((addr), (sz))))
 
-- 
1.8.1.2

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