Re: [PATCH v2 06/10] block: Make 'bytes' param of bdrv_co_{pread, pwrite, preadv, pwritev}() an int64_t

[Eric Blake]

On Fri, May 13, 2022 at 04:57:45PM +0100, Alberto Faria wrote:
> For consistency with other I/O functions, and in preparation to
> implement bdrv_{pread,pwrite}() using generated_co_wrapper.
> 
> unsigned int fits in int64_t, so all callers remain correct.

However, future callers that pass in something larger than unsigned int...

> +++ b/include/block/block_int-io.h
> @@ -56,7 +56,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
>      QEMUIOVector *qiov, size_t qiov_offset, BdrvRequestFlags flags);
>  
>  static inline int coroutine_fn bdrv_co_pread(BdrvChild *child,
> -    int64_t offset, unsigned int bytes, void *buf, BdrvRequestFlags flags)
> +    int64_t offset, int64_t bytes, void *buf, BdrvRequestFlags flags)
>  {
>      QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);

...now end up calling QEMU_IOVEC_INIT_BUF() which tries to do
.local_iov.iov_len = bytes, which can silently overflow on 32-bit
platforms where iov_len is size_t.  We need to add a code guard that
callers do not pass in too large of a buffer.

>      IO_CODE();
> @@ -65,7 +65,7 @@ static inline int coroutine_fn bdrv_co_pread(BdrvChild 
> *child,
>  }
>  
>  static inline int coroutine_fn bdrv_co_pwrite(BdrvChild *child,
> -    int64_t offset, unsigned int bytes, const void *buf, BdrvRequestFlags 
> flags)
> +    int64_t offset, int64_t bytes, const void *buf, BdrvRequestFlags flags)
>  {
>      QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);

Here as well.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org