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.

Fixes: ca3bf5d ("iommu/amd: Introduces ivrs_acpihid kernel parameter")
Cc: [email protected]
Signed-off-by: Pavel Paklov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: Pavel Paklov

drivers/iommu/amd/init.c

@@ -3664,6 +3664,14 @@ static int __init parse_ivrs_acpihid(char *str)
 	while (*uid == '0' && *(uid + 1))
 		uid++;
 
+	if (strlen(hid) >= ACPIHID_HID_LEN) {
+		pr_err("Invalid command line: hid is too long\n");
+		return 1;
+	} else if (strlen(uid) >= ACPIHID_UID_LEN) {
+		pr_err("Invalid command line: uid is too long\n");
+		return 1;
+	}
+
 	i = early_acpihid_map_size++;
 	memcpy(early_acpihid_map[i].hid, hid, strlen(hid));
 	memcpy(early_acpihid_map[i].uid, uid, strlen(uid));