From f5d83cf0eeb90fade4d5c4d17d24b8bee9ceeecc Mon Sep 17 00:00:00 2001 From: Matt Johnston Date: Thu, 6 Mar 2025 10:32:45 +0800 Subject: net: mctp: unshare packets when reassembling Ensure that the frag_list used for reassembly isn't shared with other packets. This avoids incorrect reassembly when packets are cloned, and prevents a memory leak due to circular references between fragments and their skb_shared_info. The upcoming MCTP-over-USB driver uses skb_clone which can trigger the problem - other MCTP drivers don't share SKBs. A kunit test is added to reproduce the issue. Signed-off-by: Matt Johnston Fixes: 4a992bbd3650 ("mctp: Implement message fragmentation & reassembly") Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250306-matt-mctp-usb-v1-1-085502b3dd28@codeconstruct.com.au Signed-off-by: Paolo Abeni --- net/mctp/route.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'net/mctp/route.c') diff --git a/net/mctp/route.c b/net/mctp/route.c index 3f2bd65ff5e3..4c460160914f 100644 --- a/net/mctp/route.c +++ b/net/mctp/route.c @@ -332,8 +332,14 @@ static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb) & MCTP_HDR_SEQ_MASK; if (!key->reasm_head) { - key->reasm_head = skb; - key->reasm_tailp = &(skb_shinfo(skb)->frag_list); + /* Since we're manipulating the shared frag_list, ensure it isn't + * shared with any other SKBs. + */ + key->reasm_head = skb_unshare(skb, GFP_ATOMIC); + if (!key->reasm_head) + return -ENOMEM; + + key->reasm_tailp = &(skb_shinfo(key->reasm_head)->frag_list); key->last_seq = this_seq; return 0; } -- cgit v1.2.3