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[Qemu-commits] [qemu/qemu] 348fcc: qcow2-cluster: Fix integer left shift


From: Machine user for deployment to qemu organization
Subject: [Qemu-commits] [qemu/qemu] 348fcc: qcow2-cluster: Fix integer left shift error in qco...
Date: Wed, 05 Aug 2020 08:30:30 -0700

  Branch: refs/heads/master
  Home:   https://github.com/qemu/qemu
  Commit: 348fcc4f7ace1718006e646078d88c8cd8c1d97e
      
https://github.com/qemu/qemu/commit/348fcc4f7ace1718006e646078d88c8cd8c1d97e
  Author: Tuguoyi <tu.guoyi@h3c.com>
  Date:   2020-08-05 (Wed, 05 Aug 2020)

  Changed paths:
    M block/qcow2-cluster.c

  Log Message:
  -----------
  qcow2-cluster: Fix integer left shift error in qcow2_alloc_cluster_link_l2()

When calculating the offset, the result of left shift operation will be promoted
to type int64 automatically because the left operand of + operator is uint64_t.
but the result after integer promotion may be produce an error value for us and
trigger the following asserting error.

For example, consider i=0x2000, cluster_bits=18, the result of left shift
operation will be 0x80000000. Cause argument i is of signed integer type,
the result is automatically promoted to 0xffffffff80000000 which is not
we expected

The way to trigger the assertion error:
  qemu-img create -f qcow2 -o preallocation=full,cluster_size=256k tmpdisk 10G

This patch fix it by casting @i to uint64_t before doing left shift operation

Signed-off-by: Guoyi Tu <tu.guoyi@h3c.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 81ba90fe0c014f269621c283269b42ad@h3c.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>





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