iommu/amd: Fix potential buffer overflow in parse_ivrs_acpihid

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

iommu/amd: Fix potential buffer overflow in parse_ivrs_acpihid

There is a string parsing logic error which can lead to an overflow of hid

or uid buffers. Comparing ACPIID_LEN against a total string length doesn't

take into account the lengths of individual hid and uid buffers so the

check is insufficient in some cases. For example if the length of hid

string is 4 and the length of the uid string is 260, the length of str

will be equal to ACPIID_LEN + 1 but uid string will overflow uid buffer

which size is 256.

The same applies to the hid string with length 13 and uid string with

length 250.

Check the length of hid and uid strings separately to prevent

buffer overflow.

Found by Linux Verification Center (linuxtesting.org) with SVACE.