From: Pavel Begunkov <asml.silence@gmail.com> stable inclusion from stable-v6.6.78 commit 146a185f6c05ee263db715f860620606303c4633 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBRNOR CVE: CVE-2025-21836 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=t... -------------------------------- commit 8802766324e1f5d414a81ac43365c20142e85603 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Long Li <leo.lilong@huawei.com> --- io_uring/kbuf.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 702c08c26cd4..b6fbae874f27 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -301,6 +301,12 @@ void io_destroy_buffers(struct io_ring_ctx *ctx) } } +static void io_destroy_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl) +{ + xa_erase(&ctx->io_bl_xa, bl->bgid); + 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); @@ -642,12 +648,13 @@ 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->is_mapped || !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; + if (!(reg.flags & IOU_PBUF_RING_MMAP)) ret = io_pin_pbuf_ring(®, bl); else -- 2.39.2