net: mctp i3c: Copy headers if cloned

[ Upstream commit 26db9c9ee19c36a97dbb1cfef007a3c189c4c874 ]

Use skb_cow_head() prior to modifying the tx skb. This is necessary
when the skb has been cloned, to avoid modifying other shared clones.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Fixes: c8755b29b58e ("mctp i3c: MCTP I3C driver")
Link: https://patch.msgid.link/20250306-matt-i3c-cow-head-v1-1-d5e6a5495227@codeconstruct.com.au
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/mctp/mctp-i3c.c b/drivers/net/mctp/mctp-i3c.c
index a2b15cddf46e6ba7cc3d60c53eca16567f46125d..47513ebbc68079b9c6582369702b307b87829e7c 100644 (file)
--- a/drivers/net/mctp/mctp-i3c.c
+++ b/drivers/net/mctp/mctp-i3c.c
@@ -506,10 +506,15 @@ static int mctp_i3c_header_create(struct sk_buff *skb, struct net_device *dev,
           const void *saddr, unsigned int len)
 {
        struct mctp_i3c_internal_hdr *ihdr;
+       int rc;
 
        if (!daddr || !saddr)
                return -EINVAL;
 
+       rc = skb_cow_head(skb, sizeof(struct mctp_i3c_internal_hdr));
+       if (rc)
+               return rc;
+
        skb_push(skb, sizeof(struct mctp_i3c_internal_hdr));
        skb_reset_mac_header(skb);
        ihdr = (void *)skb_mac_header(skb);