From 2545e5da080b4839dd859e3b09343a884f6ab0e3 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 17 Aug 2016 16:36:37 -0400 Subject: [PATCH] asm-generic: make copy_from_user() zero the destination properly ... in all cases, including the failing access_ok() Note that some architectures using asm-generic/uaccess.h have __copy_from_user() not zeroing the tail on failure halfway through. This variant works either way. Cc: stable@vger.kernel.org Signed-off-by: Al Viro --- include/asm-generic/uaccess.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h index 1bfa602958f2..04e21a41796a 100644 --- a/include/asm-generic/uaccess.h +++ b/include/asm-generic/uaccess.h @@ -257,11 +257,13 @@ extern int __get_user_bad(void) __attribute__((noreturn)); static inline long copy_from_user(void *to, const void __user * from, unsigned long n) { + unsigned long res = n; might_fault(); - if (access_ok(VERIFY_READ, from, n)) - return __copy_from_user(to, from, n); - else - return n; + if (likely(access_ok(VERIFY_READ, from, n))) + res = __copy_from_user(to, from, n); + if (unlikely(res)) + memset(to + (n - res), 0, res); + return res; } static inline long copy_to_user(void __user *to, -- 2.20.1