FAILED: patch "[PATCH] io_uring/register: fix ring resizing with mixed/large" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 45cd95763e198d74d369ede43aef0b1955b8dea4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026050117-strenuous-scrunch-c2ce@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 45cd95763e198d74d369ede43aef0b1955b8dea4 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 20 Apr 2026 13:41:38 -0600
Subject: [PATCH] io_uring/register: fix ring resizing with mixed/large
 SQEs/CQEs

The ring resizing only properly handles "normal" sized SQEs or CQEs, if
there are pending entries around a resize. This normally should not be
the case, but the code is supposed to handle this regardless.

For the mixed SQE/CQE cases, the current copying works fine as they
are indexed in the same way. Each half is just copied separately. But
for fixed large SQEs and CQEs, the iteration and copy need to take that
into account.

Cc: stable@kernel.org
Fixes: 79cfe9e59c2a ("io_uring/register: add IORING_REGISTER_RESIZE_RINGS")
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/register.c b/io_uring/register.c
index 24e593332d1a..dce5e2f9cf77 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -599,10 +599,20 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	if (tail - old_head > p->sq_entries)
 		goto overflow;
 	for (i = old_head; i < tail; i++) {
-		unsigned src_head = i & (ctx->sq_entries - 1);
-		unsigned dst_head = i & (p->sq_entries - 1);
+		unsigned index, dst_mask, src_mask;
+		size_t sq_size;
 
-		n.sq_sqes[dst_head] = o.sq_sqes[src_head];
+		index = i;
+		sq_size = sizeof(struct io_uring_sqe);
+		src_mask = ctx->sq_entries - 1;
+		dst_mask = p->sq_entries - 1;
+		if (ctx->flags & IORING_SETUP_SQE128) {
+			index <<= 1;
+			sq_size <<= 1;
+			src_mask = (ctx->sq_entries << 1) - 1;
+			dst_mask = (p->sq_entries << 1) - 1;
+		}
+		memcpy(&n.sq_sqes[index & dst_mask], &o.sq_sqes[index & src_mask], sq_size);
 	}
 	WRITE_ONCE(n.rings->sq.head, old_head);
 	WRITE_ONCE(n.rings->sq.tail, tail);
@@ -619,10 +629,20 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 		goto out;
 	}
 	for (i = old_head; i < tail; i++) {
-		unsigned src_head = i & (ctx->cq_entries - 1);
-		unsigned dst_head = i & (p->cq_entries - 1);
+		unsigned index, dst_mask, src_mask;
+		size_t cq_size;
 
-		n.rings->cqes[dst_head] = o.rings->cqes[src_head];
+		index = i;
+		cq_size = sizeof(struct io_uring_cqe);
+		src_mask = ctx->cq_entries - 1;
+		dst_mask = p->cq_entries - 1;
+		if (ctx->flags & IORING_SETUP_CQE32) {
+			index <<= 1;
+			cq_size <<= 1;
+			src_mask = (ctx->cq_entries << 1) - 1;
+			dst_mask = (p->cq_entries << 1) - 1;
+		}
+		memcpy(&n.rings->cqes[index & dst_mask], &o.rings->cqes[index & src_mask], cq_size);
 	}
 	WRITE_ONCE(n.rings->cq.head, old_head);
 	WRITE_ONCE(n.rings->cq.tail, tail);