On 12/22/20 9:04 PM, Josh Poimboeuf wrote:
> GCC 7 has a known bug where UBSAN ignores '-fwrapv' and generates false
> signed-overflow-UB warnings. The type mismatch between 'i' and
> 'nr_segs' in copy_compat_iovec_from_user() is causing such a warning,
> which also happens to violate uaccess rules:
>
> lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to
> __ubsan_handle_add_overflow() with UACCESS enabled
>
> Fix it by making the variable types match.
>
> This is similar to a previous commit:
>
> 29da93fea3ea ("mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on
> older GCC versions")
>
> Reported-by: Randy Dunlap <[email protected]>
> Signed-off-by: Josh Poimboeuf <[email protected]>
All good. Thanks.
Acked-by: Randy Dunlap <[email protected]> # build-tested
> ---
> lib/iov_iter.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 1635111c5bd2..2e6a42f5d1df 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1656,7 +1656,8 @@ static int copy_compat_iovec_from_user(struct iovec
> *iov,
> {
> const struct compat_iovec __user *uiov =
> (const struct compat_iovec __user *)uvec;
> - int ret = -EFAULT, i;
> + int ret = -EFAULT;
> + unsigned long i;
>
> if (!user_access_begin(uvec, nr_segs * sizeof(*uvec)))
> return -EFAULT;
>
--
~Randy
