On Fri, Jul 14, 2023 at 10:59:38AM +0200, Hanna Czenczek wrote:
> bdrv_pad_request() relies on requests' lengths not to exceed SIZE_MAX,
> which bdrv_check_qiov_request() does not guarantee.
>
> bdrv_check_request32() however will guarantee this, and both of
> bdrv_pad_request()'s callers (bdrv_co_preadv_part() and
> bdrv_co_pwritev_part()) already run it before calling
> bdrv_pad_request(). Therefore, bdrv_pad_request() can safely call
> bdrv_check_request32() without expecting error, too.
>
> In effect, this patch will not change guest-visible behavior. It is a
> clean-up to tighten a condition to match what is guaranteed by our
> callers, and which exists purely to show clearly why the subsequent
> assertion (`assert(*bytes <= SIZE_MAX)`) is always true.
>
> Note there is a difference between the interfaces of
> bdrv_check_qiov_request() and bdrv_check_request32(): The former takes
> an errp, the latter does not, so we can no longer just pass
> &error_abort. Instead, we need to check the returned value. While we
> do expect success (because the callers have already run this function),
> an assert(ret == 0) is not much simpler than just to return an error if
> it occurs, so let us handle errors by returning them up the stack now.
>
> Reported-by: Peter Maydell <peter.mayd...@linaro.org>
> Fixes: 18743311b829cafc1737a5f20bc3248d5f91ee2a
> ("block: Collapse padded I/O vecs exceeding IOV_MAX")
> Signed-off-by: Hanna Czenczek <hre...@redhat.com>
> ---
> v2:
> - Added paragraph to the commit message to express explicitly that this
> patch will not change guest-visible behavior
> - (No code changes)
> ---
> block/io.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)Thanks, applied to my block-next tree: https://gitlab.com/stefanha/qemu/commits/block-next Stefan
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