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Fri, 21 Aug 2026 03:33:24 -0700 (PDT) Received: from localhost.localdomain ([101.251.7.10]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1416ae48761sm23237958c88.12.2026.08.21.03.33.21 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 21 Aug 2026 03:33:24 -0700 (PDT) From: Laxman Acharya To: Jens Axboe Cc: Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Laxman Acharya Padhya , stable@vger.kernel.org Subject: [PATCH] io_uring/query: cap user size passed to copy_struct_to_user Date: Fri, 21 Aug 2026 16:18:17 +0545 Message-ID: <20260821103317.91437-1-acharyalaxman8848@gmail.com> X-Mailer: git-send-email 2.51.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Laxman Acharya Padhya 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 --- io_uring/query.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/io_uring/query.c b/io_uring/query.c index 88a325736992..f2b5e19e5af6 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 *dat= a, void __user *uhdr, =20 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 =3D hdr.size; hdr.size =3D min(hdr.size, IO_MAX_QUERY_SIZE); udata =3D u64_to_user_ptr(hdr.query_data); --=20 2.51.2