Re: FAILED: patch "[PATCH] io_uring/rsrc: require cloned buffers to share accounting" failed to apply to 6.12-stable tree

[Jens Axboe <axboe@kernel.dk>]

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On 1/30/25 4:38 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 6.12-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-6.12.y
> git checkout FETCH_HEAD
> git cherry-pick -x 19d340a2988d4f3e673cded9dde405d727d7e248
> # <resolve conflicts, build, test, etc.>
> git commit -s
> git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025013011-scenic-crazed-e3c8@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Here's a 6.12-stable version of this patch.

-- 
Jens Axboe

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From 605dc321522f4334849759d9585bef54dc60994f Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
Date: Tue, 14 Jan 2025 18:49:00 +0100
Subject: [PATCH] io_uring/rsrc: require cloned buffers to share accounting
 contexts

Commit 19d340a2988d4f3e673cded9dde405d727d7e248 upstream.

When IORING_REGISTER_CLONE_BUFFERS is used to clone buffers from uring
instance A to uring instance B, where A and B use different MMs for
accounting, the accounting can go wrong:
If uring instance A is closed before uring instance B, the pinned memory
counters for uring instance B will be decremented, even though the pinned
memory was originally accounted through uring instance A; so the MM of
uring instance B can end up with negative locked memory.

Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/r/CAG48ez1zez4bdhmeGLEFxtbFADY4Czn3CV0u9d_TMcbvRA01bg@mail.gmail.com
Fixes: 7cc2a6eadcd7 ("io_uring: add IORING_REGISTER_COPY_BUFFERS method")
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20250114-uring-check-accounting-v1-1-42e4145aa743@google.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/rsrc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 6f3b6de230bd..a67bae350416 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1153,6 +1153,13 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx
 	struct io_rsrc_data *data;
 	int i, ret, nbufs;
 
+	/*
+	 * Accounting state is shared between the two rings; that only works if
+	 * both rings are accounted towards the same counters.
+	 */
+	if (ctx->user != src_ctx->user || ctx->mm_account != src_ctx->mm_account)
+		return -EINVAL;
+
 	/*
 	 * Drop our own lock here. We'll setup the data we need and reference
 	 * the source buffers, then re-grab, check, and assign at the end.
-- 
2.47.2