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

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 <[email protected]>.

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 '<[email protected]>' --in-reply-to '2025013011-scenic-crazed-e3c8@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 19d340a2988d4f3e673cded9dde405d727d7e248 Mon Sep 17 00:00:00 2001
From: Jann Horn <[email protected]>
Date: Tue, 14 Jan 2025 18:49:00 +0100
Subject: [PATCH] io_uring/rsrc: require cloned buffers to share accounting
contexts

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.

index 964a47c8d85e..688e277f0335 100644
@@ -928,6 +928,13 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx
 	int i, ret, off, nr;
 	unsigned int 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;
+
 	/* if offsets are given, must have nr specified too */
 	if (!arg->nr && (arg->dst_off || arg->src_off))
 		return -EINVAL;

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

Jens Axboe

From 605dc321522f4334849759d9585bef54dc60994f Mon Sep 17 00:00:00 2001
From: Jann Horn <[email protected]>
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.

---
 io_uring/rsrc.c | 7 +++++++
 1 file changed, 7 insertions(+)

index 6f3b6de230bd..a67bae350416 100644
@@ -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

Now queued up, thanks!

greg k-h