Re: FAILED: patch "[PATCH] io_uring/net: commit partial buffers on retry" failed to apply to 6.6-stable tree

[Jens Axboe <axboe@kernel.dk>]

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On 8/15/25 9:26 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 6.6-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> To reproduce the conflict and resubmit, you may use the following commands:
> 
> git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
> git checkout FETCH_HEAD
> git cherry-pick -x 41b70df5b38bc80967d2e0ed55cc3c3896bba781
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025081549-shorter-borrower-941d@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Here's one for 6.6-stable.

-- 
Jens Axboe

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From c16cb4e2a4b1a487ca7feae5931dfb22ac495b76 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 12 Aug 2025 08:30:11 -0600
Subject: [PATCH] io_uring/net: commit partial buffers on retry

Commit a6dfda7da5c65b282c1663326be16e57aec3d1bd upstream.

Ring provided buffers are potentially only valid within the single
execution context in which they were acquired. io_uring deals with this
and invalidates them on retry. But on the networking side, if
MSG_WAITALL is set, or if the socket is of the streaming type and too
little was processed, then it will hang on to the buffer rather than
recycle or commit it. This is problematic for two reasons:

1) If someone unregisters the provided buffer ring before a later retry,
   then the req->buf_list will no longer be valid.

2) If multiple sockers are using the same buffer group, then multiple
   receives can consume the same memory. This can cause data corruption
   in the application, as either receive could land in the same
   userspace buffer.

Fix this by disallowing partial retries from pinning a provided buffer
across multiple executions, if ring provided buffers are used.

Cc: stable@vger.kernel.org
Reported-by: pt x <superman.xpt@gmail.com>
Fixes: c56e022c0a27 ("io_uring: add support for user mapped provided buffer ring")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/net.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/io_uring/net.c b/io_uring/net.c
index e455f051e62e..e7f8a79e049c 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -351,6 +351,13 @@ static int io_setup_async_addr(struct io_kiocb *req,
 	return -EAGAIN;
 }
 
+static void io_net_kbuf_recyle(struct io_kiocb *req)
+{
+	req->flags |= REQ_F_PARTIAL_IO;
+	if (req->flags & REQ_F_BUFFER_RING)
+		io_kbuf_recycle_ring(req);
+}
+
 int io_sendmsg_prep_async(struct io_kiocb *req)
 {
 	int ret;
@@ -442,7 +449,7 @@ int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags)
 			kmsg->msg.msg_controllen = 0;
 			kmsg->msg.msg_control = NULL;
 			sr->done_io += ret;
-			req->flags |= REQ_F_PARTIAL_IO;
+			io_net_kbuf_recyle(req);
 			return io_setup_async_msg(req, kmsg, issue_flags);
 		}
 		if (ret == -ERESTARTSYS)
@@ -521,7 +528,7 @@ int io_send(struct io_kiocb *req, unsigned int issue_flags)
 			sr->len -= ret;
 			sr->buf += ret;
 			sr->done_io += ret;
-			req->flags |= REQ_F_PARTIAL_IO;
+			io_net_kbuf_recyle(req);
 			return io_setup_async_addr(req, &__address, issue_flags);
 		}
 		if (ret == -ERESTARTSYS)
@@ -891,7 +898,7 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 		}
 		if (ret > 0 && io_net_retry(sock, flags)) {
 			sr->done_io += ret;
-			req->flags |= REQ_F_PARTIAL_IO;
+			io_net_kbuf_recyle(req);
 			return io_setup_async_msg(req, kmsg, issue_flags);
 		}
 		if (ret == -ERESTARTSYS)
@@ -991,7 +998,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 			sr->len -= ret;
 			sr->buf += ret;
 			sr->done_io += ret;
-			req->flags |= REQ_F_PARTIAL_IO;
+			io_net_kbuf_recyle(req);
 			return -EAGAIN;
 		}
 		if (ret == -ERESTARTSYS)
@@ -1235,7 +1242,7 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
 			zc->len -= ret;
 			zc->buf += ret;
 			zc->done_io += ret;
-			req->flags |= REQ_F_PARTIAL_IO;
+			io_net_kbuf_recyle(req);
 			return io_setup_async_addr(req, &__address, issue_flags);
 		}
 		if (ret == -ERESTARTSYS)
@@ -1306,7 +1313,7 @@ int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags)
 
 		if (ret > 0 && io_net_retry(sock, flags)) {
 			sr->done_io += ret;
-			req->flags |= REQ_F_PARTIAL_IO;
+			io_net_kbuf_recyle(req);
 			return io_setup_async_msg(req, kmsg, issue_flags);
 		}
 		if (ret == -ERESTARTSYS)
-- 
2.50.1