RE: [PATCH net] tipc: fix integer overflow in tipc_recvmsg() and tipc_recvstream()

Subject: [PATCH net] tipc: fix integer overflow in tipc_recvmsg() and
tipc_recvstream()

In tipc_recvmsg(), the copy length is computed as:

 copy = min_t(int, dlen - offset, buflen);

buflen is size_t but min_t(int, ...) casts it to int. When buflen exceeds INT_MAX
(e.g. 0xFFFFFFFF via io_uring provided buffers), it wraps negative, wins the
comparison, and the negative copy length propagates to simple_copy_to_iter()
where int-to-size_t promotion makes it SIZE_MAX, triggering a WARN_ON.
tipc_recvstream() has the same pattern.

 Kernel panic - not syncing: kernel: panic_on_warn set ...
 RIP: 0010:simple_copy_to_iter+0x9e/0xd0 (net/core/datagram.c:521)
 Call Trace:
  __skb_datagram_iter+0x123/0x8b0 (net/core/datagram.c:402)
  skb_copy_datagram_iter+0x77/0x1a0 (net/core/datagram.c:534)
  tipc_recvmsg+0x3d7/0xe80 (net/tipc/socket.c:1934)
  io_recvmsg+0x47e/0xda0

Fix by changing min_t(int, ...) to min_t(size_t, ...) in both functions. The result is
always <= (dlen - offset), which is bounded by TIPC maximum message size
(0x1ffff bytes), so the implicit narrowing on assignment to int copy is always
safe.

Fixes: e9f8b10101c6 ("tipc: refactor function tipc_sk_recvmsg()")
Fixes: ec8a09fbbeff ("tipc: refactor function tipc_sk_recv_stream()")
Reported-by: AutonomousCodeSecurity@microsoft.com
Signed-off-by: Cen Zhang (Microsoft) <redacted>
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Reviewed-by: Tung Nguyen <redacted>