[PATCH 6/6] io_uring/register: fix ring resizing with mixed/large SQEs/CQEs

[Jens Axboe <axboe@kernel.dk>]

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")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/register.c | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

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);
-
-		n.sq_sqes[dst_head] = o.sq_sqes[src_head];
+		unsigned index, dst_mask, src_mask;
+		size_t sq_size;
+
+		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);
-
-		n.rings->cqes[dst_head] = o.rings->cqes[src_head];
+		unsigned index, dst_mask, src_mask;
+		size_t cq_size;
+
+		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);
-- 
2.53.0