FAILED: patch "[PATCH] io_uring/kbuf: reallocate buf lists on upgrade" failed to apply to 6.13-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.13-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-6.13.y
git checkout FETCH_HEAD
git cherry-pick -x 8802766324e1f5d414a81ac43365c20142e85603
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025021855-snugly-hacked-a8fa@gregkh' --subject-prefix 'PATCH 6.13.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8802766324e1f5d414a81ac43365c20142e85603 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Wed, 12 Feb 2025 13:46:46 +0000
Subject: [PATCH] io_uring/kbuf: reallocate buf lists on upgrade

IORING_REGISTER_PBUF_RING can reuse an old struct io_buffer_list if it
was created for legacy selected buffer and has been emptied. It violates
the requirement that most of the field should stay stable after publish.
Always reallocate it instead.

Cc: stable@vger.kernel.org
Reported-by: Pumpkin Chang <pumpkin@devco.re>
Fixes: 2fcabce2d7d34 ("io_uring: disallow mixed provided buffer group registrations")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 04bf493eecae..8e72de7712ac 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -415,6 +415,13 @@ void io_destroy_buffers(struct io_ring_ctx *ctx)
 	}
 }
 
+static void io_destroy_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
+{
+	scoped_guard(mutex, &ctx->mmap_lock)
+		WARN_ON_ONCE(xa_erase(&ctx->io_bl_xa, bl->bgid) != bl);
+	io_put_bl(ctx, bl);
+}
+
 int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
@@ -636,12 +643,13 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 		/* if mapped buffer ring OR classic exists, don't allow */
 		if (bl->flags & IOBL_BUF_RING || !list_empty(&bl->buf_list))
 			return -EEXIST;
-	} else {
-		free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
-		if (!bl)
-			return -ENOMEM;
+		io_destroy_bl(ctx, bl);
 	}
 
+	free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
+	if (!bl)
+		return -ENOMEM;
+
 	mmap_offset = (unsigned long)reg.bgid << IORING_OFF_PBUF_SHIFT;
 	ring_size = flex_array_size(br, bufs, reg.ring_entries);