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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>,
	Luo Likang <luolikang@nsfocus.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-media@vger.kernel.org,
	linux1394-devel@lists.sourceforge.net,
	Yang Yanchao <yangyanchao6@huawei.com>,
	Salvatore Bonaccorso <carnil@debian.org>,
	security@kernel.org, linux-distros@vs.openwall.org
Subject: [PATCH v2 RESEND] media: firewire: firedtv-avc: fix a buffer overflow in avc_ca_pmt()
Date: Mon, 16 Aug 2021 10:27:22 +0300	[thread overview]
Message-ID: <20210816072721.GA10534@kili> (raw)
In-Reply-To: <YRoNTX3Krtw9NdkI@eldamar.lan>

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().  Added a check in fdtv_ca_pmt() to
prevent that.

Cc: stable@vger.kernel.org
Reported-by: Luo Likang <luolikang@nsfocus.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
RESEND: this patch got lost somehow.

v2: Change the limit in fdtv_ca_pmt() from "sizeof(msg->msg) - 4" to
"sizeof(msg->msg) - data_pos".

Oh, another thing is the data_length calculation in fdtv_ca_pmt() seems
very suspicous.  Reading more than 4 bytes in the loop will lead to
shift wrapping.

 drivers/media/firewire/firedtv-avc.c | 14 +++++++++++---
 drivers/media/firewire/firedtv-ci.c  |  2 ++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/media/firewire/firedtv-avc.c b/drivers/media/firewire/firedtv-avc.c
index 2bf9467b917d..71991f8638e6 100644
--- a/drivers/media/firewire/firedtv-avc.c
+++ b/drivers/media/firewire/firedtv-avc.c
@@ -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;
 			}
diff --git a/drivers/media/firewire/firedtv-ci.c b/drivers/media/firewire/firedtv-ci.c
index 9363d005e2b6..2d6992ac5dd6 100644
--- a/drivers/media/firewire/firedtv-ci.c
+++ b/drivers/media/firewire/firedtv-ci.c
@@ -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);
 }
-- 
2.30.2


  reply	other threads:[~2021-08-16  7:28 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <000001d73031$d5304480$7f90cd80$@nsfocus.com>
2021-04-14  8:57 ` [PATCH] " Dan Carpenter
2021-04-19 21:42   ` Kees Cook
2021-06-07 15:23   ` [PATCH v2] " Dan Carpenter
2021-07-16  9:28     ` Petr Mladek
2021-07-19 10:25   ` [PATCH] " Dan Carpenter
2021-07-29 10:32   ` Greg KH
2021-08-16  7:01     ` Salvatore Bonaccorso
2021-08-16  7:27       ` Dan Carpenter [this message]
2021-09-01 10:40         ` [PATCH v2 RESEND] " Dan Carpenter
2021-09-12 13:14           ` Salvatore Bonaccorso
2021-09-12 18:26             ` Linus Torvalds
2021-09-13  2:50               ` Michael Ellerman
2021-09-13 13:23               ` Mauro Carvalho Chehab
2021-09-19 18:45                 ` Salvatore Bonaccorso
2021-10-11  7:04                   ` Salvatore Bonaccorso
2021-10-11  9:42                     ` [PATCH] " Dan Carpenter

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