From: William Kucharski
Sent: 14 November 2018 10:35
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?
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))
Ugg... you don't want a double test.
I'd guess that a length of zero is likely, but a usercopy that includes the highest address is going to be invalid because it is a kernel address (on most archs, and probably illegal on others). What you really want to do is add 'ptr + len' and check the carry flag.
David
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