From: Vladimir Sementsov-Ogievskiy Date: Thu, 12 Mar 2020 11:19:49 +0300 Subject: block/io: fix bdrv_co_do_copy_on_readv Git-commit: 4ab78b19189a81038e744728ed949d09aa477550 Prior to 1143ec5ebf4 it was OK to qemu_iovec_from_buf() from aligned-up buffer to original qiov, as qemu_iovec_from_buf() will stop at qiov end anyway. But after 1143ec5ebf4 we assume that bdrv_co_do_copy_on_readv works on part of original qiov, defined by qiov_offset and bytes. So we must not touch qiov behind qiov_offset+bytes bound. Fix it. Cc: qemu-stable@nongnu.org # v4.2 Fixes: 1143ec5ebf4 Signed-off-by: Vladimir Sementsov-Ogievskiy Reviewed-by: John Snow Message-id: 20200312081949.5350-1-vsementsov@virtuozzo.com Signed-off-by: Stefan Hajnoczi Signed-off-by: Bruce Rogers --- block/io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/io.c b/block/io.c index d1f1ee9138c7af82352e9277f22b..c2c3aab9ee3d1d4d494ce98a6d8b 100644 --- a/block/io.c +++ b/block/io.c @@ -1395,7 +1395,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child, if (!(flags & BDRV_REQ_PREFETCH)) { qemu_iovec_from_buf(qiov, qiov_offset + progress, bounce_buffer + skip_bytes, - pnum - skip_bytes); + MIN(pnum - skip_bytes, bytes - progress)); } } else if (!(flags & BDRV_REQ_PREFETCH)) { /* Read directly into the destination */