Re: FAILED: patch "[PATCH] io_uring/net: harden multishot termination case for recv" failed to apply to 6.6-stable tree

[Jens Axboe <axboe@kernel.dk>]

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On 10/7/24 11:30 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 c314094cb4cfa6fc5a17f4881ead2dfebfa717a7
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2024100732-pessimist-ambiguous-58e3@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..

Ditto for 6.6-stable.

-- 
Jens Axboe

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From 68d694ede220209c8f9fad33c76ad41373826a03 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 26 Sep 2024 07:08:10 -0600
Subject: [PATCH] io_uring/net: harden multishot termination case for recv

If the recv returns zero, or an error, then it doesn't matter if more
data has already been received for this buffer. A condition like that
should terminate the multishot receive. Rather than pass in the
collected return value, pass in whether to terminate or keep the recv
going separately.

Note that this isn't a bug right now, as the only way to get there is
via setting MSG_WAITALL with multishot receive. And if an application
does that, then -EINVAL is returned anyway. But it seems like an easy
bug to introduce, so let's make it a bit more explicit.

Link: https://github.com/axboe/liburing/issues/1246
Cc: stable@vger.kernel.org
Fixes: b3fdea6ecb55 ("io_uring: multishot recv")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/io_uring/net.c b/io_uring/net.c
index cf1060fb04f4..7412904387bf 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -930,6 +930,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 	int ret, min_ret = 0;
 	bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
 	size_t len = sr->len;
+	bool mshot_finished;
 
 	if (!(req->flags & REQ_F_POLLED) &&
 	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
@@ -999,6 +1000,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 		req_set_fail(req);
 	}
 
+	mshot_finished = ret <= 0;
 	if (ret > 0)
 		ret += sr->done_io;
 	else if (sr->done_io)
@@ -1006,7 +1008,7 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 	else
 		io_kbuf_recycle(req, issue_flags);
 
-	if (!io_recv_finish(req, &ret, &msg, ret <= 0, issue_flags))
+	if (!io_recv_finish(req, &ret, &msg, mshot_finished, issue_flags))
 		goto retry_multishot;
 
 	return ret;
-- 
2.45.2