| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 108/118] asm-generic: make copy_from_user() zero the destination properly | Date | Thu, 22 Sep 2016 19:30:08 +0200 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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From: Al Viro <viro@zeniv.linux.org.uk>
commit 2545e5da080b4839dd859e3b09343a884f6ab0e3 upstream.
... 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.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- include/asm-generic/uaccess.h | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/include/asm-generic/uaccess.h +++ b/include/asm-generic/uaccess.h @@ -261,11 +261,13 @@ extern int __get_user_bad(void) __attrib 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,
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