[PATCH 6.1.y 1/8] io_uring/net: keep recvmsg buffer select length within MAX_RW_COUNT

[Jens Axboe <axboe@kernel.dk>]

From: Yichong Chen <chenyichong@uniontech.com>

Commit 18d3f56eb6e6500a65d81cf265f0fe74fd9ecab6 upstream.

io_recvmsg() takes the transfer length from the ring provided buffer when
sqe->len is 0, and such a buffer can be up to 4G. min_ret is an int, so 2G
or more makes it negative and the (ret < min_ret) block is skipped, and the
oversized length reaches the socket layer unchanged: an empty socket then
completes with 0 instead of arming poll, and a short read is reported as
complete. Clamp the length to MAX_RW_COUNT, as io_recv() does.

Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers")
Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
Link: https://patch.msgid.link/20261023112209.87979-1-chenyichong@uniontech.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[axboe: 6.1 has the older io_buffer_select() interface]
---
 io_uring/net.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/io_uring/net.c b/io_uring/net.c
index cc25cbb27e5d..86a18814c628 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -805,6 +805,7 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 		buf = io_buffer_select(req, &len, issue_flags);
 		if (!buf)
 			return -ENOBUFS;
+		len = min_t(size_t, len, MAX_RW_COUNT);
 
 		if (req->flags & REQ_F_APOLL_MULTISHOT) {
 			ret = io_recvmsg_prep_multishot(kmsg, sr, &buf, &len);
-- 
2.56.0