path: root/net/mptcp
diff options
authorPaolo Abeni <>2021-05-11 19:13:51 +0200
committerDavid S. Miller <>2021-05-11 16:19:17 -0700
commit29249eac5225429b898f278230a6ca2baa1ae154 (patch)
treeda66634d5393a645fe2279d0e0a75c022304ee87 /net/mptcp
parentdf6f8237036938d48b7705681c170566c00593fa (diff)
mptcp: fix data stream corruption
Maxim reported several issues when forcing a TCP transparent proxy to use the MPTCP protocol for the inbound connections. He also provided a clean reproducer. The problem boils down to 'mptcp_frag_can_collapse_to()' assuming that only MPTCP will use the given page_frag. If others - e.g. the plain TCP protocol - allocate page fragments, we can end-up re-using already allocated memory for mptcp_data_frag. Fix the issue ensuring that the to-be-expanded data fragment is located at the current page frag end. v1 -> v2: - added missing fixes tag (Mat) Closes: Reported-and-tested-by: Maxim Galaganov <> Fixes: 18b683bff89d ("mptcp: queue data for mptcp level retransmission") Signed-off-by: Paolo Abeni <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'net/mptcp')
1 files changed, 6 insertions, 0 deletions
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 29a2d690d8d5..2d21a4793d9d 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -879,12 +879,18 @@ static bool mptcp_skb_can_collapse_to(u64 write_seq,
+/* we can append data to the given data frag if:
+ * - there is space available in the backing page_frag
+ * - the data frag tail matches the current page_frag free offset
+ * - the data frag end sequence number matches the current write seq
+ */
static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
const struct page_frag *pfrag,
const struct mptcp_data_frag *df)
return df && pfrag->page == df->page &&
pfrag->size - pfrag->offset > 0 &&
+ pfrag->offset == (df->offset + df->data_len) &&
df->data_seq + df->data_len == msk->write_seq;