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asm-generic: make copy_from_user() zero the destination properly

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... 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 <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2016-08-17 16:36:37 -04:00
parent 2561d309df
commit 2545e5da08
1 changed files with 6 additions and 4 deletions
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10
include/asm-generic/uaccess.h
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@@ -257,11 +257,13 @@ extern int __get_user_bad(void) __attribute__((noreturn));
static inline long copy_from_user(void *to, static inline long copy_from_user(void *to,
const void __user * from, unsigned long n) const void __user * from, unsigned long n)
{ {
unsigned long res = n;
might_fault(); might_fault();
if (access_ok(VERIFY_READ, from, n)) if (likely(access_ok(VERIFY_READ, from, n)))
return __copy_from_user(to, from, n); res = __copy_from_user(to, from, n);
else if (unlikely(res))
return n; memset(to + (n - res), 0, res);
return res;
} }
static inline long copy_to_user(void __user *to, static inline long copy_to_user(void __user *to,