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io_uring/query: cap user size passed to copy_struct_to_user

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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: c265ae75f9 ("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>
This commit is contained in:
Laxman Acharya Padhya
2026-08-21 16:18:17 +05:45
committed by Jens Axboe
parent 66498c75b4
commit ba77efee1b
1 changed files with 3 additions and 0 deletions
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3
io_uring/query.c
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@@ -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);