6.16-stable review patch. If anyone has any objections, please let me know.
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From: Jeremy Kerr jk@codeconstruct.com.au
[ Upstream commit 773b27a8a2f00ce3134e92e50ea4794a98ba2b76 ]
As of commit f5d83cf0eeb9 ("net: mctp: unshare packets when reassembling"), we skb_unshare() in mctp_frag_queue(). The unshare may invalidate the original skb pointer, so we need to treat the skb as entirely owned by the fraq queue, even on failure.
Fixes: f5d83cf0eeb9 ("net: mctp: unshare packets when reassembling") Signed-off-by: Jeremy Kerr jk@codeconstruct.com.au Link: https://patch.msgid.link/20250829-mctp-skb-unshare-v1-1-1c28fe10235a@codecon... Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/mctp/route.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-)
diff --git a/net/mctp/route.c b/net/mctp/route.c index d9c8e5a5f9ce9..19ff259d7bc43 100644 --- a/net/mctp/route.c +++ b/net/mctp/route.c @@ -325,6 +325,7 @@ static void mctp_skb_set_flow(struct sk_buff *skb, struct mctp_sk_key *key) {} static void mctp_flow_prepare_output(struct sk_buff *skb, struct mctp_dev *dev) {} #endif
+/* takes ownership of skb, both in success and failure cases */ static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb) { struct mctp_hdr *hdr = mctp_hdr(skb); @@ -334,8 +335,10 @@ static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb) & MCTP_HDR_SEQ_MASK;
if (!key->reasm_head) { - /* Since we're manipulating the shared frag_list, ensure it isn't - * shared with any other SKBs. + /* Since we're manipulating the shared frag_list, ensure it + * isn't shared with any other SKBs. In the cloned case, + * this will free the skb; callers can no longer access it + * safely. */ key->reasm_head = skb_unshare(skb, GFP_ATOMIC); if (!key->reasm_head) @@ -349,10 +352,10 @@ static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb) exp_seq = (key->last_seq + 1) & MCTP_HDR_SEQ_MASK;
if (this_seq != exp_seq) - return -EINVAL; + goto err_free;
if (key->reasm_head->len + skb->len > mctp_message_maxlen) - return -EINVAL; + goto err_free;
skb->next = NULL; skb->sk = NULL; @@ -366,6 +369,10 @@ static int mctp_frag_queue(struct mctp_sk_key *key, struct sk_buff *skb) key->reasm_head->truesize += skb->truesize;
return 0; + +err_free: + kfree_skb(skb); + return -EINVAL; }
static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb) @@ -476,18 +483,16 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb) * key isn't observable yet */ mctp_frag_queue(key, skb); + skb = NULL;
/* if the key_add fails, we've raced with another * SOM packet with the same src, dest and tag. There's * no way to distinguish future packets, so all we - * can do is drop; we'll free the skb on exit from - * this function. + * can do is drop. */ rc = mctp_key_add(key, msk); - if (!rc) { + if (!rc) trace_mctp_key_acquire(key); - skb = NULL; - }
/* we don't need to release key->lock on exit, so * clean up here and suppress the unlock via @@ -505,8 +510,7 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb) key = NULL; } else { rc = mctp_frag_queue(key, skb); - if (!rc) - skb = NULL; + skb = NULL; } }
@@ -516,17 +520,16 @@ static int mctp_route_input(struct mctp_route *route, struct sk_buff *skb) */
/* we need to be continuing an existing reassembly... */ - if (!key->reasm_head) + if (!key->reasm_head) { rc = -EINVAL; - else + } else { rc = mctp_frag_queue(key, skb); + skb = NULL; + }
if (rc) goto out_unlock;
- /* we've queued; the queue owns the skb now */ - skb = NULL; - /* end of message? deliver to socket, and we're done with * the reassembly/response key */