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FAILED: patch "[PATCH] media: firewire: firedtv-avc: fix a buffer overflow in" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Nov 3, 2021

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Stable branch Media (V4L/DVB) Firewire media drivers (firedtv)
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The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 35d2969ea3c7d32aee78066b1f3cf61a0d935a4e Mon Sep 17 00:00:00 2001
From: Dan Carpenter <[email protected]>
Date: Mon, 7 Jun 2021 17:23:48 +0200
Subject: [PATCH] media: firewire: firedtv-avc: fix a buffer overflow in
avc_ca_pmt()

The bounds checking in avc_ca_pmt() is not strict enough. It should be checking "read_pos + 4" because it's reading 5 bytes. If the "es_info_length" is non-zero then it reads a 6th byte so there needs to be an additional check for that.

I also added checks for the "write_pos". I don't think these are required because "read_pos" and "write_pos" are tied together so checking one ought to be enough. But they make the code easier to understand for me. The check on write_pos is:

	if (write_pos + 4 >= sizeof(c->operand) - 4) {

The first "+ 4" is because we're writing 5 bytes and the last " - 4" is to leave space for the CRC.

The other problem is that "length" can be invalid. It comes from "data_length" in fdtv_ca_pmt().

Cc [email protected]
Reported-by Luo Likang <[email protected]>
Signed-off-by Dan Carpenter <[email protected]>
Signed-off-by Hans Verkuil <[email protected]>
Signed-off-by Mauro Carvalho Chehab <[email protected]>
drivers/media/firewire/firedtv-avc.c +11 -3
index 2bf9467b917d..71991f8638e6 100644
@@ -1165,7 +1165,11 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
 		read_pos += program_info_length;
 		write_pos += program_info_length;
 	}
-	while (read_pos < length) {
+	while (read_pos + 4 < length) {
+		if (write_pos + 4 >= sizeof(c->operand) - 4) {
+			ret = -EINVAL;
+			goto out;
+		}
 		c->operand[write_pos++] = msg[read_pos++];
 		c->operand[write_pos++] = msg[read_pos++];
 		c->operand[write_pos++] = msg[read_pos++];

@@ -1177,13 +1181,17 @@ int avc_ca_pmt(struct firedtv *fdtv, char *msg, int length)
 		c->operand[write_pos++] = es_info_length >> 8;
 		c->operand[write_pos++] = es_info_length & 0xff;
 		if (es_info_length > 0) {
+			if (read_pos >= length) {
+				ret = -EINVAL;
+				goto out;
+			}
 			pmt_cmd_id = msg[read_pos++];
 			if (pmt_cmd_id != 1 && pmt_cmd_id != 4)
 				dev_err(fdtv->device, "invalid pmt_cmd_id %d at stream level\n",
 					pmt_cmd_id);
 
-			if (es_info_length > sizeof(c->operand) - 4 -
-					     write_pos) {
+			if (es_info_length > sizeof(c->operand) - 4 - write_pos ||
+			    es_info_length > length - read_pos) {
 				ret = -EINVAL;
 				goto out;
 			}
drivers/media/firewire/firedtv-ci.c +2 -0
index 9363d005e2b6..e0d57e09dab0 100644
@@ -134,6 +134,8 @@ static int fdtv_ca_pmt(struct firedtv *fdtv, void *arg)
 	} else {
 		data_length = msg->msg[3];
 	}
+	if (data_length > sizeof(msg->msg) - data_pos)
+		return -EINVAL;
 
 	return avc_ca_pmt(fdtv, &msg->msg[data_pos], data_length);
 }