[4.2.y-ckt stable] Patch "MIPS: uaccess: Fix strlen_user with EVA" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    MIPS: uaccess: Fix strlen_user with EVA

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From fb1229972c3196a566e9eb00e7e610c3aec8f28f Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan at imgtec.com>
Date: Wed, 5 Aug 2015 16:41:37 +0100
Subject: MIPS: uaccess: Fix strlen_user with EVA

commit 5dc62fdd8383afbd2faca6b6e6ea1052b45b0124 upstream.

The strlen_user() function calls __strlen_kernel_asm in both branches of
the eva_kernel_access() conditional. For EVA it should be calling
__strlen_user_eva for user accesses, otherwise it will load from the
kernel address space instead of the user address space, and the access
checking will likely be ineffective at preventing it due to EVA's
overlapping user and kernel address spaces.

This was found after extending the test_user_copy module to cover user
string access functions, which gave the following error with EVA:

test_user_copy: illegal strlen_user passed

Fortunately the use of strlen_user() has been all but eradicated from
the mainline kernel, so only out of tree modules could be affected.

Fixes: e3a9b07a9caf ("MIPS: asm: uaccess: Add EVA support for str*_user operations")
Signed-off-by: James Hogan <james.hogan at imgtec.com>
Cc: Markos Chandras <markos.chandras at imgtec.com>
Cc: Paul Burton <paul.burton at imgtec.com>
Cc: Leonid Yegoshin <leonid.yegoshin at imgtec.com>
Cc: linux-mips at linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10842/
Signed-off-by: Ralf Baechle <ralf at linux-mips.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/mips/include/asm/uaccess.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index 5305d69..3f959c0 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -1384,7 +1384,7 @@ static inline long strlen_user(const char __user *s)
 		might_fault();
 		__asm__ __volatile__(
 			"move\t$4, %1\n\t"
-			__MODULE_JAL(__strlen_kernel_asm)
+			__MODULE_JAL(__strlen_user_asm)
 			"move\t%0, $2"
 			: "=r" (res)
 			: "r" (s)
--
1.9.1