[PATCH] iommu/amd: Fix potential buffer overflow in parse_ivrs_acpihid

[Pavel Paklov]

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: ca3bf5d47cec ("iommu/amd: Introduces ivrs_acpihid kernel parameter")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Pavel Paklov <Pavel.Paklov@xxxxxxxxxxxxxxx>
---
 drivers/iommu/amd/init.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index cb536d372b12..fb82f8035c0f 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3677,6 +3677,14 @@ 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));
-- 
2.43.0