Hi Li,

On 02/03/2026 06:26, Li Xiasong wrote:

syzbot reported a soft lockup in mptcp_recvmsg() [0].

When receiving data with MSG_PEEK | MSG_WAITALL flags, the skb is not
removed from the sk_receive_queue. This causes sk_wait_data() to always
find available data and never perform actual waiting, leading to a soft
lockup.

Fix this by adding a 'last' parameter to track the last peeked skb.
This allows sk_wait_data() to make informed waiting decisions and prevent
infinite loops when MSG_PEEK is used.

Thank you for the patch! I will check why sk_wait_data() was not used
with the last SKB before.

By chance, do you have a reproducer that you could eventually share please?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.