net: mctp: fix don't require received header reserved bits to be zero

From the MCTP Base specification (DSP0236 v1.2.1), the first byte of
the MCTP header contains a 4 bit reserved field, and 4 bit version.

On our current receive path, we require those 4 reserved bits to be
zero, but the 9500-8i card is non-conformant, and may set these
reserved bits.

DSP0236 states that the reserved bits must be written as zero, and
ignored when read. While the device might not conform to the former,
we should accept these message to conform to the latter.

Relax our check on the MCTP version byte to allow non-zero bits in the
reserved field.

Fixes: 889b7da23abf ("mctp: Add initial routing framework")
Signed-off-by: Yuan Zhaoming <yuanzm2@lenovo.com>
Cc: stable@vger.kernel.org
Acked-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20260417141340.5306-1-yuanzhaoming901030@126.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/mctp.h b/include/net/mctp.h
index e1e0a69afdcef7f0924523757010e75ea53e8e7c..d8bf9074110d9d6284a5d63660e1d06a99338227 100644 (file)
--- a/include/net/mctp.h
+++ b/include/net/mctp.h
@@ -26,6 +26,9 @@ struct mctp_hdr {
 #define MCTP_VER_MIN   1
 #define MCTP_VER_MAX   1
 
+/* Definitions for ver field */
+#define MCTP_HDR_VER_MASK      GENMASK(3, 0)
+
 /* Definitions for flags_seq_tag field */
 #define MCTP_HDR_FLAG_SOM      BIT(7)
 #define MCTP_HDR_FLAG_EOM      BIT(6)

diff --git a/net/mctp/route.c b/net/mctp/route.c
index 26fb8c6bbad2cb4ae686e38db29b34f14f3894aa..1f3dccbb7aedba7886dd092cda06d8cb5fc66d93 100644 (file)
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -441,6 +441,7 @@ static int mctp_dst_input(struct mctp_dst *dst, struct sk_buff *skb)
        unsigned long f;
        u8 tag, flags;
        int rc;
+       u8 ver;
 
        msk = NULL;
        rc = -EINVAL;
@@ -467,7 +468,8 @@ static int mctp_dst_input(struct mctp_dst *dst, struct sk_buff *skb)
        netid = mctp_cb(skb)->net;
        skb_pull(skb, sizeof(struct mctp_hdr));
 
-       if (mh->ver != 1)
+       ver = mh->ver & MCTP_HDR_VER_MASK;
+       if (ver < MCTP_VER_MIN || ver > MCTP_VER_MAX)
                goto out;
 
        flags = mh->flags_seq_tag & (MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM);
@@ -1317,6 +1319,7 @@ static int mctp_pkttype_receive(struct sk_buff *skb, struct net_device *dev,
        struct mctp_dst dst;
        struct mctp_hdr *mh;
        int rc;
+       u8 ver;
 
        rcu_read_lock();
        mdev = __mctp_dev_get(dev);
@@ -1334,7 +1337,8 @@ static int mctp_pkttype_receive(struct sk_buff *skb, struct net_device *dev,
 
        /* We have enough for a header; decode and route */
        mh = mctp_hdr(skb);
-       if (mh->ver < MCTP_VER_MIN || mh->ver > MCTP_VER_MAX)
+       ver = mh->ver & MCTP_HDR_VER_MASK;
+       if (ver < MCTP_VER_MIN || ver > MCTP_VER_MAX)
                goto err_drop;
 
        /* source must be valid unicast or null; drop reserved ranges and