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From: Pavel Skripkin <paskripkin@gmail.com>
To: David Laight <David.Laight@ACULAB.COM>,
	'Dan Carpenter' <dan.carpenter@oracle.com>
Cc: "Larry.Finger@lwfinger.net" <Larry.Finger@lwfinger.net>,
	"phil@philpotter.co.uk" <phil@philpotter.co.uk>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"straube.linux@gmail.com" <straube.linux@gmail.com>,
	"fmdefrancesco@gmail.com" <fmdefrancesco@gmail.com>,
	"linux-staging@lists.linux.dev" <linux-staging@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 3/6] staging: r8188eu: add error handling of rtw_read8
Date: Fri, 27 Aug 2021 11:22:57 +0300	[thread overview]
Message-ID: <b4d8ed8f-db03-a5b1-bb7a-0f086ea8ffbd@gmail.com> (raw)
In-Reply-To: <dc133b63e1f54f45a19e67d75a6fcb40@AcuMS.aculab.com>

On 8/27/21 11:14 AM, David Laight wrote:
> From: Dan Carpenter
>> Sent: 26 August 2021 12:21
> ...
>> > > > ...
>> > > > > +		len += snprintf(page + len, count - len,
>> > > > > "rtw_read8(0x%x)=0x%x\n",
>> > > > > +				proc_get_read_addr, (u8) tmp);
>> > > >
>> > > > That is broken.
>> > > >
>> > >
>> > > Don't get it, sorry. Previous code did exactly the same thing, but
>> > > didn't check if read() was successful.
>> >
>> > Look up the return value of snprintf().
>> >
>> 
>> It's hard to understand what you are saying.  I think you are confusing
>> libc snprintf with the kernel snprintf?  In libc the snprintf function
>> can return negatives but in the kernel it cannot.  This is not going
>> to change.  Any code which checks for negative snprintf returns in the
>> kernel is wrong and should be fixed.
>> 
>> Anyway, the code works fine.  snprintf here is going to return a number
>> between 18-32 range.  It's not going to overflow the PAGE_SIZE buffer.
> 
> IIRC it is also in a loop ...
> 
> Maybe, but the idiom is just broken.
> Largely the result of snprintf() is never the value you are looking
> for and should be ignored.
> 

AFAIK, snprintf return value is largely used in sysfs at least.

$ grep -Ir "= snprintf" | wc -l
1200

Anyway, I will convert this dead code to sysfs interface and maybe 
snprintf will go away...



Thank you for your help and comments


> Userspace fprintf() is even worse.
> If you care about the write failing you need to call fflush()
> and then ferror() (typically before fclose()).
> 
> Fortunately I've never seen a 'must check' attribute on it.
> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
> 


With regards,
Pavel Skripkin

  reply	other threads:[~2021-08-27  8:23 UTC|newest]

Thread overview: 118+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-20 17:07 [PATCH RFC 0/3] staging: r8188eu: avoid uninit value bugs Pavel Skripkin
2021-08-20 17:07 ` [PATCH RFC 1/3] staging: r8188eu: add proper rtw_read* error handling Pavel Skripkin
2021-08-20 21:50   ` Pavel Skripkin
2021-08-20 23:41   ` Phillip Potter
2021-08-21  5:55   ` Fabio M. De Francesco
2021-08-21 10:35     ` Pavel Skripkin
2021-08-21 12:11       ` Fabio M. De Francesco
2021-08-20 17:07 ` [PATCH RFC 2/3] staging: r8188eu: add error handling to ReadFuse Pavel Skripkin
2021-08-20 23:51   ` Phillip Potter
2021-08-21  3:59     ` Fabio M. De Francesco
2021-08-20 17:07 ` [PATCH RFC 3/3] staging: r8188eu: add error argument to read_macreg Pavel Skripkin
2021-08-20 23:18   ` Phillip Potter
2021-08-21 10:38     ` Pavel Skripkin
2021-08-20 23:12 ` [PATCH RFC 0/3] staging: r8188eu: avoid uninit value bugs Phillip Potter
2021-08-21 10:42   ` Pavel Skripkin
2021-08-22  9:53 ` Fabio M. De Francesco
2021-08-22 10:09   ` Pavel Skripkin
2021-08-22 10:59     ` Fabio M. De Francesco
2021-08-22 11:34       ` Fabio M. De Francesco
2021-08-22 12:10       ` Pavel Skripkin
2021-08-22 12:39         ` Greg KH
2021-08-22 12:50           ` Pavel Skripkin
2021-08-22 13:06             ` Greg KH
2021-08-22 13:21           ` Fabio M. De Francesco
2021-08-22 13:30             ` Greg KH
2021-08-22 13:31             ` Pavel Skripkin
2021-08-22 14:35               ` [PATCH RFC v2 0/6] " Pavel Skripkin
2021-08-22 14:35                 ` [PATCH RFC v2 1/6] staging: r8188eu: remove {read,write}_macreg Pavel Skripkin
2021-08-22 14:35                 ` [PATCH RFC v2 2/6] staging: r8188eu: add helper macro for printing registers Pavel Skripkin
2021-08-22 14:35                 ` [PATCH RFC v2 3/6] staging: r8188eu: add error handling of rtw_read8 Pavel Skripkin
2021-08-22 14:35                 ` [PATCH RFC v2 4/6] staging: r8188eu: add error handling of rtw_read16 Pavel Skripkin
2021-08-22 14:36                 ` [PATCH RFC v2 5/6] staging: r8188eu: add error handling of rtw_read32 Pavel Skripkin
2021-08-23 23:33                   ` Phillip Potter
2021-08-24  0:10                     ` Fabio M. De Francesco
2021-08-24  6:40                       ` Pavel Skripkin
2021-08-24  8:38                         ` Fabio M. De Francesco
2021-08-24  8:47                           ` Pavel Skripkin
2021-08-24  8:53                             ` Pavel Skripkin
2021-08-24  9:46                               ` Fabio M. De Francesco
2021-08-24 22:10                               ` Phillip Potter
2021-08-24 22:07                             ` Phillip Potter
2021-08-24  6:53                     ` Pavel Skripkin
2021-08-24  7:25                     ` [PATCH v3 0/6] staging: r8188eu: avoid uninit value bugs Pavel Skripkin
2021-08-24  7:27                       ` [PATCH v3 1/6] staging: r8188eu: remove {read,write}_macreg Pavel Skripkin
2021-08-26 10:39                         ` Greg KH
2021-08-26 10:40                         ` Greg KH
2021-08-24  7:27                       ` [PATCH v3 2/6] staging: r8188eu: add helper macro for printing registers Pavel Skripkin
2021-08-26 10:37                         ` Greg KH
2021-08-24  7:27                       ` [PATCH v3 3/6] staging: r8188eu: add error handling of rtw_read8 Pavel Skripkin
2021-08-25 12:05                         ` kernel test robot
2021-08-25 12:17                           ` Pavel Skripkin
2021-08-25 12:51                             ` Dan Carpenter
2021-08-25 13:02                               ` Pavel Skripkin
2021-08-25 13:34                                 ` Dan Carpenter
2021-08-25 13:44                                   ` Pavel Skripkin
2021-08-25 17:11                                     ` Nick Desaulniers
2021-08-26 11:08                                       ` Dan Carpenter
2021-08-25 23:45                         ` Fabio M. De Francesco
2021-08-26  5:13                           ` Pavel Skripkin
2021-08-26  8:21                         ` David Laight
2021-08-26  8:27                           ` Pavel Skripkin
2021-08-26 10:19                             ` David Laight
2021-08-26 11:21                               ` Dan Carpenter
2021-08-27  8:14                                 ` David Laight
2021-08-27  8:22                                   ` Pavel Skripkin [this message]
2021-08-27  9:07                         ` Dan Carpenter
2021-08-27  9:16                           ` Pavel Skripkin
2021-08-27  9:23                             ` Dan Carpenter
2021-08-30 11:21                         ` kernel test robot
2021-08-24  7:27                       ` [PATCH v3 4/6] staging: r8188eu: add error handling of rtw_read16 Pavel Skripkin
2021-08-25  4:35                         ` Fabio M. De Francesco
2021-08-25  8:22                           ` Pavel Skripkin
2021-08-25  9:48                             ` Fabio M. De Francesco
2021-08-25  9:55                               ` Pavel Skripkin
2021-08-25 10:06                                 ` Dan Carpenter
2021-08-25 10:13                                   ` Pavel Skripkin
2021-08-25 10:38                                     ` Dan Carpenter
2021-08-25 10:41                                       ` Pavel Skripkin
2021-08-25 11:06                                       ` Fabio M. De Francesco
2021-08-25 11:11                                         ` Fabio M. De Francesco
2021-08-25 11:31                                         ` Dan Carpenter
2021-08-25 12:11                                           ` Fabio M. De Francesco
2021-08-25 10:51                                 ` Fabio M. De Francesco
2021-08-26 10:50                         ` Greg KH
2021-08-26 10:58                           ` Pavel Skripkin
2021-08-24  7:27                       ` [PATCH v3 5/6] staging: r8188eu: add error handling of rtw_read32 Pavel Skripkin
2021-08-25  4:40                         ` Fabio M. De Francesco
2021-08-26  8:51                         ` David Laight
2021-08-26  9:22                           ` Pavel Skripkin
2021-08-26  9:27                             ` Pavel Skripkin
2021-08-26 10:22                               ` David Laight
2021-08-26 10:55                                 ` Pavel Skripkin
2021-08-26 10:59                                   ` David Laight
2021-08-26 20:03                                     ` Pavel Skripkin
2021-08-27  7:12                                       ` gregkh
2021-08-27  7:16                                         ` Pavel Skripkin
2021-08-24  7:27                       ` [PATCH v3 6/6] staging: r8188eu: make ReadEFuse return an int Pavel Skripkin
2021-08-25 10:13                       ` [PATCH v3 0/6] staging: r8188eu: avoid uninit value bugs Fabio M. De Francesco
2021-08-27  7:49                       ` Kari Argillander
2021-08-27  7:52                         ` Pavel Skripkin
2021-08-24  6:58                   ` [PATCH RFC v2 5/6] staging: r8188eu: add error handling of rtw_read32 Dan Carpenter
2021-08-24  7:01                     ` Pavel Skripkin
2021-08-24 15:07                       ` Fabio M. De Francesco
2021-08-22 14:36                 ` [PATCH RFC v2 6/6] staging: r8188eu: make ReadEFuse return an int Pavel Skripkin
2021-08-22 15:30                 ` [PATCH RFC v2 0/6] staging: r8188eu: avoid uninit value bugs Pavel Skripkin
2021-08-22 16:05                   ` Michael Straube
2021-08-22 16:26                     ` Pavel Skripkin
2021-08-22 23:52                       ` Phillip Potter
2021-08-22 17:36                 ` Fabio M. De Francesco
2021-08-22 17:38                   ` Pavel Skripkin
2021-08-22 20:06                     ` Fabio M. De Francesco
2021-08-22 20:19                       ` Pavel Skripkin
2021-08-23  0:12                 ` Phillip Potter
2021-08-23  6:38                   ` Pavel Skripkin
2021-08-23  6:44                   ` Pavel Skripkin
2021-08-22 16:03               ` [PATCH RFC 0/3] " Fabio M. De Francesco
2021-08-22 16:15                 ` Pavel Skripkin
2021-08-22 15:04             ` Phillip Potter

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