io_handle_query_entry() clamps hdr.size for the inbound copy_from_user() but keeps the original user value as usize. copy_struct_to_user() uses that usize and, when it is larger than the kernel result, clear_user()s the trailing bytes. As hdr.size is a __u32, a query can request nearly 4 GiB of zeroing, including on the error path where res_size stays 0. The interface is reachable without a ring via IORING_REGISTER_QUERY. Reject sizes larger than PAGE_SIZE, as recommended for copy_struct_* interfaces. Fixes: c265ae75f900 ("io_uring: introduce io_uring querying") Cc: stable@vger.kernel.org # 6.18+ Signed-off-by: Laxman Acharya Padhya <acharyalaxman8848@gmail.com> Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de> Link: https://patch.msgid.link/20260821103317.91437-1-acharyalaxman8848@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>