From e8a8a6972c5075e6057264c45614d13f9e0307e5 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Tue, 2 May 2017 19:41:06 +0100 Subject: metag/uaccess: Check access_ok in strncpy_from_user 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 Signed-off-by: James Hogan Cc: linux-metag@vger.kernel.org Signed-off-by: Greg Kroah-Hartman diff --git a/arch/metag/include/asm/uaccess.h b/arch/metag/include/asm/uaccess.h index ed6cd90..3db3812 100644 --- 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) * -- cgit v0.10.2