From: Kevin Wolf <kwolf@redhat.com>
To: Tuguoyi <tu.guoyi@h3c.com>
Cc: peter.maydell@linaro.org, Chengchiwen <chengchiwen@h3c.com>,
"qemu-block@nongnu.org" <qemu-block@nongnu.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"mreitz@redhat.com" <mreitz@redhat.com>,
Gaoliang <liang_gao@h3c.com>, Wangyong <wang.yongD@h3c.com>
Subject: Re: [PATCH] qcow2-cluster: Fix integer left shift error in qcow2_alloc_cluster_link_l2()
Date: Wed, 5 Aug 2020 15:39:53 +0200 [thread overview]
Message-ID: <20200805133953.GC4679@linux.fritz.box> (raw)
In-Reply-To: <81ba90fe0c014f269621c283269b42ad@h3c.com>
Am 05.08.2020 um 11:22 hat Tuguoyi geschrieben:
> 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: Kevin Wolf <kwolf@redhat.com>
next prev parent reply other threads:[~2020-08-05 13:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-05 9:22 [PATCH] qcow2-cluster: Fix integer left shift error in qcow2_alloc_cluster_link_l2() Tuguoyi
2020-08-05 13:33 ` [PATCH for-5.1?] " Eric Blake
2020-08-05 13:39 ` Kevin Wolf [this message]
2020-08-05 13:44 ` [PATCH] " Alberto Garcia
2020-08-05 13:45 ` Alberto Garcia
2020-08-05 14:16 ` Kevin Wolf
2020-08-05 14:32 ` Alberto Garcia
2020-08-05 15:21 ` Peter Maydell
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