linux-kernel - Re: [External] : RE: [PATCH 2/3] drivers: hv: vmbus: Fix sscanf format specifier in target_cpu

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Message-ID: <2871837b-b766-49d5-b7a8-49af7f367781@oracle.com>
Date: Mon, 15 Sep 2025 18:31:02 +0530
From: ALOK TIWARI <alok.a.tiwari@...cle.com>
To: Michael Kelley <mhklinux@...look.com>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "decui@...rosoft.com" <decui@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [External] : RE: [PATCH 2/3] drivers: hv: vmbus: Fix sscanf
 format specifier in target_cpu_store()



On 9/14/2025 9:57 AM, Michael Kelley wrote:
> From: Alok Tiwari<alok.a.tiwari@...cle.com> Sent: Saturday, September 13, 2025 12:25 PM
>> The target_cpu_store() function parses the target CPU from the sysfs
>> buffer using sscanf(). The format string currently uses "%uu", which
>> is invalid and causes incorrect parsing.
> The %uu format string definitely looks invalid, but I'm not seeing
> incorrect parsing.  For example, this command works:
> 
> # echo 5 >/sys/bus/vmbus/devices/<uuid>/channels/<nn>/cpu
> 
> and the target cpu is indeed changed to "5".  A two-digit value also
> works:
> 
> # echo 14 >/sys/bus/vmbus/devices/<uuid>/channels/<nn>/cpu
> 
> What are the details of the incorrect parsing that you are seeing?
> 
> Michael

Thanks Michael,

You are right, The compiler ignores the extra "u", so there is no 
incorrect parsing at runtime. My wording was misleading. This change 
should be treated as a cleanup/cosmetic change rather than a real fix.


Thanks,
Alok