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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 5.5 101/176] io_uring: fix 32-bit compatability with sendmsg/recvmsg
Date:   Tue,  3 Mar 2020 18:42:45 +0100
Message-Id: <20200303174316.529389059@linuxfoundation.org>
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From: Jens Axboe <axboe@kernel.dk>

commit d876836204897b6d7d911f942084f69a1e9d5c4d upstream.

We must set MSG_CMSG_COMPAT if we're in compatability mode, otherwise
the iovec import for these commands will not do the right thing and fail
the command with -EINVAL.

Found by running the test suite compiled as 32-bit.

Cc: stable@vger.kernel.org
Fixes: aa1fa28fc73e ("io_uring: add support for recvmsg()")
Fixes: 0fa03c624d8f ("io_uring: add support for sendmsg()")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/io_uring.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2166,6 +2166,11 @@ static int io_sendmsg_prep(struct io_kio
 	sr->msg_flags = READ_ONCE(sqe->msg_flags);
 	sr->msg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 
+#ifdef CONFIG_COMPAT
+	if (req->ctx->compat)
+		sr->msg_flags |= MSG_CMSG_COMPAT;
+#endif
+
 	if (!io)
 		return 0;
 
@@ -2258,6 +2263,11 @@ static int io_recvmsg_prep(struct io_kio
 	sr->msg_flags = READ_ONCE(sqe->msg_flags);
 	sr->msg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 
+#ifdef CONFIG_COMPAT
+	if (req->ctx->compat)
+		sr->msg_flags |= MSG_CMSG_COMPAT;
+#endif
+
 	if (!io)
 		return 0;