[PATCH] io_uring/net: keep recv buffer select length within MAX_RW_COUNT

[Tamaki Yanagawa <ty@000ty.net>]

Since commit dcbd1c054848 ("io_uring/net: let io_recv_buf_select return
the length of the buffer region"), io_recv_buf_select() returns the
selected length as an int. For a non-bundle recv with sqe->len == 0 the
length comes from the ring provided buffer, which can be up to 4G, so a
buffer of 2G or more makes io_recv() fail the request with a bogus
negative result (e.g. -2147483648) instead of receiving into it. Clamp
the length to MAX_RW_COUNT, which import_ubuf() limits the transfer to
anyway.

Fixes: dcbd1c054848 ("io_uring/net: let io_recv_buf_select return the length of the buffer region")
Signed-off-by: Tamaki Yanagawa <ty@000ty.net>
Assisted-by: Claude:claude-opus-5-5
---
 io_uring/net.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/io_uring/net.c b/io_uring/net.c
index f5f4f3ce6e..c82ea46cf5 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1178,6 +1178,8 @@ static int io_recv_buf_select(struct io_kiocb *req, struct io_async_msghdr *kmsg
 		*sel = io_buffer_select(req, &len, sr->buf_group, issue_flags);
 		if (!sel->addr)
 			return -ENOBUFS;
+		/* ring provided buffers can be up to 4G, keep len an int */
+		len = min_t(size_t, len, MAX_RW_COUNT);
 		sr->buf = sel->addr;
 		sr->len = len;
 map_ubuf:

base-commit: fddcf4c5321b3ea5f72166c3fd36a9d1c34f80c7
-- 
2.52.0.windows.1