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From: "Jan Beulich" <JBeulich@suse.com>
To: Ian Campbell <ian.campbell@citrix.com>,
	Joshua Otto <jtotto@uwaterloo.ca>
Cc: wei.liu2@citrix.com, stefano.stabellini@eu.citrix.com,
	george.dunlap@eu.citrix.com, dario.faggioli@citrix.com,
	ian.jackson@eu.citrix.com, czylin@uwaterloo.ca,
	xen-devel@lists.xen.org, hjarmstr@uwaterloo.ca
Subject: Re: [PATCH 3/5] ns16550: widen an integer constant for Coverity.
Date: Wed, 06 Jan 2016 02:26:23 -0700	[thread overview]
Message-ID: <568CEBD002000078000C3D17@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1451925380.13361.189.camel@citrix.com>

>>> On 04.01.16 at 17:36, <ian.campbell@citrix.com> wrote:
> On Mon, 2015-12-28 at 00:16 -0500, Joshua Otto wrote:
>> Fix CID 1343302 by widening a constant used with uart_param.reg_shift to
>> avoid overflow for large values of reg_shift.
> 
> A reg_shift large enough to actually expose this would be infeasibly large
> (since it would imply a UART taking practically the entire virtual address
> space of the processor).
> 
> So while Coverity is likely correct here, it is probably also a bit
> misguided in the context.
> 
> I don't especially object to this change as means to quieten coverity, but
> perhaps checking for some sane limit to reg_shift would also serve to
> quieten coverity?

Indeed I'd prefer an alternative change to be found, as 64-bit
arithmetic is quite pointless here.

>> Signed-off-by: Harley Armstrong <hjarmstr@uwaterloo.ca>
>> ---
>>  xen/drivers/char/ns16550.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
>> index bc24015..546bba1 100644
>> --- a/xen/drivers/char/ns16550.c
>> +++ b/xen/drivers/char/ns16550.c
>> @@ -913,7 +913,7 @@ pci_uart_config(struct ns16550 *uart, bool_t
>> skip_amt, unsigned int bar_idx)
>>                           * Force length of mmio region to be at least
>>                           * 8 bytes times (1 << reg_shift)
>>                          */
>> -                        if ( size < (0x8 * (1 << uart_param[p].reg_shift)) )
>> +                        if ( size < (0x8 * (1ull << uart_param[p].reg_shift)) )
> 
> It looks from the surrounding code like
>   ... < (0x8 * ((u64)1 << uart_param[p].reg_shift)) )
> 
> would be the preferred way of tackling this.

If we were to really stay with a change to this line, then the
multiplication should go away altogether, since just a shift
will always suffice.

Jan

  reply	other threads:[~2016-01-06  9:26 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-12-04 20:26 Taking on a Xen development project jtotto
2015-12-10 10:59 ` Wei Liu
2015-12-10 17:23 ` Andrew Cooper
2015-12-12  2:19   ` Yang Hongyang
2015-12-12 22:30     ` Joshua Otto
2015-12-12 23:02       ` Andrew Cooper
2015-12-14 22:49         ` Joshua Otto
2015-12-11 13:52 ` Ian Campbell
2015-12-12 22:07   ` Joshua Otto
2015-12-14 11:08     ` Ian Campbell
2015-12-14 22:59       ` Joshua Otto
2015-12-15 15:48         ` Ian Campbell
2015-12-28  5:16       ` Coverity tidying Joshua Otto
2015-12-28  5:16         ` [PATCH 1/5] libxl: tidy libxl_get_scheduler() according to CODING_STYLE Joshua Otto
2016-01-04 16:23           ` Ian Campbell
2016-01-05  8:20             ` Dario Faggioli
2016-01-19  5:57               ` [PATCH v2 " Chester Lin
2016-01-19  9:14                 ` Dario Faggioli
2016-01-19 11:28                 ` Wei Liu
2016-01-19 11:35                   ` Ian Campbell
2015-12-28  5:16         ` [PATCH 2/5] libxl: make GC_FREE reachable in libxl_get_scheduler() Joshua Otto
2016-01-04 16:29           ` Ian Campbell
2016-01-05  8:49             ` Dario Faggioli
2016-01-05 11:16               ` Ian Campbell
2016-01-19  5:57                 ` [PATCH v2 " Chester Lin
2016-01-19  9:08                   ` Dario Faggioli
2016-01-19 14:15                   ` Ian Jackson
2015-12-28  5:16         ` [PATCH 3/5] ns16550: widen an integer constant for Coverity Joshua Otto
2016-01-04 16:36           ` Ian Campbell
2016-01-06  9:26             ` Jan Beulich [this message]
2016-01-19  5:57               ` [PATCH v2 3/5] n16550: add sanity check for reg_shift Chester Lin
2016-01-19 13:32                 ` Jan Beulich
2016-01-25  0:41                   ` czylin
2015-12-28  5:16         ` [PATCH 4/5] credit: remove pointless local variable initialization Joshua Otto
2015-12-28  5:16         ` [PATCH 5/5] libxl: Add explicit cast to libxl_psr_cat_set_cbm Joshua Otto
2016-01-04 16:40           ` Ian Campbell
2016-01-19  5:58             ` [PATCH v2 " Chester Lin
2016-01-19  8:34               ` Dario Faggioli
2016-01-19 14:06               ` Ian Jackson
2016-01-19 14:21                 ` Ian Campbell
2016-01-19 14:28                   ` Dario Faggioli
2016-01-19 14:33                     ` Ian Jackson
2016-01-19 14:31                   ` George Dunlap
2016-01-19 14:31                 ` Ian Campbell
2016-01-19 14:35                   ` Ian Jackson
2017-01-12 18:08                     ` George Dunlap
2017-01-13  9:05                       ` Dario Faggioli
2015-12-28  9:34         ` Coverity tidying Andrew Cooper
2016-01-01  3:14           ` [PATCH] svm: rephrase local variable use for Coverity Joshua Otto
2016-01-06 13:24             ` Jan Beulich
2016-01-06 14:33               ` Boris Ostrovsky

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