From ba77efee1b95b4ad7559b1cdbe7cd7fa36dca95b Mon Sep 17 00:00:00 2001 From: Laxman Acharya Padhya Date: Fri, 21 Aug 2026 16:18:17 +0545 Subject: io_uring/query: cap user size passed to copy_struct_to_user 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 Reviewed-by: Gabriel Krisman Bertazi Link: https://patch.msgid.link/20260821103317.91437-1-acharyalaxman8848@gmail.com Signed-off-by: Jens Axboe --- io_uring/query.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/io_uring/query.c b/io_uring/query.c index 4321f0b94b4b..7bce2ec162c1 100644 --- a/io_uring/query.c +++ b/io_uring/query.c @@ -76,6 +76,9 @@ static int io_handle_query_entry(union io_query_data *data, void __user *uhdr, if (copy_from_user(&hdr, uhdr, sizeof(hdr))) return -EFAULT; + /* copy_struct_to_user() zeros up to usize bytes */ + if (hdr.size > PAGE_SIZE) + return -E2BIG; usize = hdr.size; hdr.size = min(hdr.size, IO_MAX_QUERY_SIZE); udata = u64_to_user_ptr(hdr.query_data); -- cgit v1.2.3