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From: David Laight <David.Laight@ACULAB.COM>
To: 'Dan Carpenter' <dan.carpenter@oracle.com>,
	"kys@microsoft.com" <kys@microsoft.com>
Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
	"olaf@aepfle.de" <olaf@aepfle.de>,
	"apw@canonical.com" <apw@canonical.com>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	"sthemmin@microsoft.com" <sthemmin@microsoft.com>,
	"Michael.H.Kelley@microsoft.com" <Michael.H.Kelley@microsoft.com>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	Haiyang Zhang <haiyangz@microsoft.com>
Subject: RE: [PATCH V2 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1
Date: Thu, 18 Oct 2018 15:08:34 +0000	[thread overview]
Message-ID: <872b63db79e5468f97dded249c4478f9@AcuMS.aculab.com> (raw)
In-Reply-To: <20181018063230.v6hp5e3agk62c3s3@mwanda>

From: Dan Carpenter
> Sent: 18 October 2018 07:33
> 
> On Thu, Oct 18, 2018 at 05:09:32AM +0000, kys@linuxonhyperv.com wrote:
> > From: Dexuan Cui <decui@microsoft.com>
> >
> > The patch fixes:
> >
> > hv_kvp_daemon.c: In function 'kvp_set_ip_info':
> > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes
> > into a destination of size 4096
> >
> > The "(unsigned int)str_len" is to avoid:
> >
> > hv_kvp_daemon.c:1309:30: warning: comparison of integer expressions of
> > different signedness: 'int' and 'long unsigned int' [-Wsign-compare]

I usually use 'str_len + 0u' rather than a cast.

> Ugh...  Any tool with the most basic flow analysis would realize this
> was a false positive.  We use at least three static analyzers which
> catch signedness bugs.  Can we turn off GCC's warning on this until they
> improve it a bit?

Yes, would be nice if it attempted to follow the valid domain of variables.

I recently had to change:
	unsigned char a, b;
	unsigned int c;
	...
	if (a + b < c)
To stop a 'signedness' warning.

	David

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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


  reply	other threads:[~2018-10-18 15:08 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-18  5:08 [PATCH V2 0/5] Drivers: hv: Miscellaneous fixes kys
2018-10-18  5:09 ` [PATCH V2 1/5] Drivers: hv: vmbus: Get rid of unnecessary state in hv_context kys
2018-10-18  5:09   ` [PATCH V2 2/5] hv_utils: update name in struct hv_driver util_drv kys
2018-10-18  5:09   ` [PATCH V2 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up kys
2018-10-24 15:37     ` Michael Kelley
2018-10-31 23:23       ` Dexuan Cui
2018-11-01 18:56         ` gregkh
2018-11-01 19:22           ` Dexuan Cui
2018-11-02  4:54             ` gregkh
2018-11-11  4:18               ` Dexuan Cui
2018-11-11 17:09                 ` gregkh
2018-11-02 21:55           ` KY Srinivasan
2018-11-01 19:38     ` Haiyang Zhang
2018-10-18  5:09   ` [PATCH V2 4/5] Drivers: hv: kvp: Use %u to print U32 kys
2018-10-18  5:09   ` [PATCH V2 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1 kys
2018-10-18  6:32     ` Dan Carpenter
2018-10-18 15:08       ` David Laight [this message]
2018-10-24 15:04   ` [PATCH V2 1/5] Drivers: hv: vmbus: Get rid of unnecessary state in hv_context Michael Kelley

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