This is a note to let you know that I've just added the patch titled
metag/uaccess: Check access_ok in strncpy_from_user
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
metag-uaccess-check-access_ok-in-strncpy_from_user.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3a158a62da0673db918b53ac1440845a5b64fd90 Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@xxxxxxxxxx>
Date: Tue, 2 May 2017 19:41:06 +0100
Subject: metag/uaccess: Check access_ok in strncpy_from_user
From: James Hogan <james.hogan@xxxxxxxxxx>
commit 3a158a62da0673db918b53ac1440845a5b64fd90 upstream.
The metag implementation of strncpy_from_user() doesn't validate the src
pointer, which could allow reading of arbitrary kernel memory. Add a
short access_ok() check to prevent that.
Its still possible for it to read across the user/kernel boundary, but
it will invariably reach a NUL character after only 9 bytes, leaking
only a static kernel address being loaded into D0Re0 at the beginning of
__start, which is acceptable for the immediate fix.
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: linux-metag@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/metag/include/asm/uaccess.h | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/arch/metag/include/asm/uaccess.h
+++ b/arch/metag/include/asm/uaccess.h
@@ -194,8 +194,13 @@ do {
extern long __must_check __strncpy_from_user(char *dst, const char __user *src,
long count);
-#define strncpy_from_user(dst, src, count) __strncpy_from_user(dst, src, count)
-
+static inline long
+strncpy_from_user(char *dst, const char __user *src, long count)
+{
+ if (!access_ok(VERIFY_READ, src, 1))
+ return -EFAULT;
+ return __strncpy_from_user(dst, src, count);
+}
/*
* Return the size of a string (including the ending 0)
*
Patches currently in stable-queue which might be from james.hogan@xxxxxxxxxx are
queue-4.4/metag-uaccess-check-access_ok-in-strncpy_from_user.patch
queue-4.4/metag-uaccess-fix-access_ok.patch