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);