On Wed, Nov 14, 2018 at 4:35 AM, William Kucharski william.kucharski@oracle.com wrote:
On Nov 13, 2018, at 5:51 PM, Isaac J. Manjarres isaacm@codeaurora.org wrote:
diff --git a/mm/usercopy.c b/mm/usercopy.c index 852eb4e..0293645 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -151,7 +151,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, bool to_user) { /* Reject if object wraps past end of memory. */
if (ptr + n < ptr)
if (ptr + (n - 1) < ptr) usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n);I'm being paranoid, but is it possible this routine could ever be passed "n" set to zero?
It's a single-use inline, and zero is tested just before getting called:
/* Skip all tests if size is zero. */ if (!n) return;
/* Check for invalid addresses. */ check_bogus_address((const unsigned long)ptr, n, to_user);
If so, it will erroneously abort indicating a wrapped address as (n - 1) wraps to ULONG_MAX.
Easily fixed via:
if ((n != 0) && (ptr + (n - 1) < ptr))
Agreed. Thanks for noticing this!
-Kees