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qemu-kvm/SOURCES/kvm-block-Fix-pad_request-s...

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From 547f6bf93734f7c13675eebb93273ef2273f7c31 Mon Sep 17 00:00:00 2001
From: Hanna Czenczek <hreitz@redhat.com>
Date: Fri, 14 Jul 2023 10:59:38 +0200
Subject: [PATCH 5/9] block: Fix pad_request's request restriction
RH-Author: Hanna Czenczek <hreitz@redhat.com>
RH-MergeRequest: 189: block: Split padded I/O vectors exceeding IOV_MAX
RH-Bugzilla: 2174676
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Commit: [5/5] e8abc0485f6e0608a1ec55143ff40a14d273dfc8 (hreitz/qemu-kvm-c-9-s)
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.maydell@linaro.org>
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-id: 20230714085938.202730-1-hreitz@redhat.com
Fixes: 18743311b829cafc1737a5f20bc3248d5f91ee2a
("block: Collapse padded I/O vecs exceeding IOV_MAX")
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block/io.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/block/io.c b/block/io.c
index 4e8e90208b..807c9fb720 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1708,7 +1708,11 @@ static int bdrv_pad_request(BlockDriverState *bs,
int sliced_niov;
size_t sliced_head, sliced_tail;
- bdrv_check_qiov_request(*offset, *bytes, *qiov, *qiov_offset, &error_abort);
+ /* Should have been checked by the caller already */
+ ret = bdrv_check_request32(*offset, *bytes, *qiov, *qiov_offset);
+ if (ret < 0) {
+ return ret;
+ }
if (!bdrv_init_padding(bs, *offset, *bytes, write, pad)) {
if (padded) {
@@ -1721,7 +1725,7 @@ static int bdrv_pad_request(BlockDriverState *bs,
&sliced_head, &sliced_tail,
&sliced_niov);
- /* Guaranteed by bdrv_check_qiov_request() */
+ /* Guaranteed by bdrv_check_request32() */
assert(*bytes <= SIZE_MAX);
ret = bdrv_create_padded_qiov(bs, pad, sliced_iov, sliced_niov,
sliced_head, *bytes);
--
2.39.3