CVE-2022-48828

In the Linux kernel, the following vulnerability has been resolved:

NFSD: Fix ia_size underflow

iattr::ia_size is a loff_t, which is a signed 64-bit type. NFSv3 and

NFSv4 both define file size as an unsigned 64-bit type. Thus there

is a range of valid file size values an NFS client can send that is

already larger than Linux can handle.

Currently decode_fattr4() dumps a full u64 value into ia_size. If

that value happens to be larger than S64_MAX, then ia_size

underflows. I'm about to fix up the NFSv3 behavior as well, so let's

catch the underflow in the common code path: nfsd_setattr().