[ECOS] Error in io\serial\current\src\common\tty.c

[ECOS] Error in io\serial\current\src\common\tty.c

[Alexander Hering]

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Hello,

we have found an error in the tty driver.
When i press the backspace key, when no more characters are in the
buffer, the last input is printed again.

In function tty_read size is declared as unsigned int, and must not be
tested against a value below zero.

====> cyg_uint32 size, clen;

      if ((c == '\b') || (c == 0x7F)) {
        size -= 2;  // erase one character + 'backspace' char
====>   if (size < 0) size = 0;
      
Greetings

	Alex

-- 
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Alexander Hering		Hansastraße 32
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RE: [ECOS] Error in io\serial\current\src\common\tty.c

[Gary Thomas]

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A fix for this problem has already been installed.  

We suggest that you use CVS to keep track of the [very] latest 
eCos sources.  See our web page ( http://sourceware.cygnus.com/ecos )
for the details.

On 28-Jan-00 Alexander Hering wrote:
> Hello,
> 
> we have found an error in the tty driver.
> When i press the backspace key, when no more characters are in the
> buffer, the last input is printed again.
> 
> In function tty_read size is declared as unsigned int, and must not be
> tested against a value below zero.
> 
> ====> cyg_uint32 size, clen;
> 
>       if ((c == '\b') || (c == 0x7F)) {
>         size -= 2;  // erase one character + 'backspace' char
> ====>   if (size < 0) size = 0;
>       
> Greetings
> 
>       Alex
> 
> -- 
> Fraunhofer-Einrichtung
>               Systeme der Kommunikationstechnik
> 
> Alexander Hering              Hansastraße 32
> Dipl.-Ing.                    D-80686 München
>                               Telefon: +49(0)89/547088-37
> E-Mail: Hering@esk.fhg.de     Telefax: +49(0)89/547088-25

Re: [ECOS] Error in io\serial\current\src\common\tty.c

[Alexander Hering]

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This is a copy of the actual version in CVS:

    cyg_uint32 size, clen;

    if ((c == '\b') || (c == 0x7F)) {
    size -= 2;  // erase one character + 'backspace' char
==> if (size < 0) {
       size = 0;
    } else if (priv->dev_info.tty_in_flags & CYG_TTY_IN_FLAGS_ECHO) {
       clen = 3;
       cyg_io_write(chan, "\b \b", &clen);
   }

There is still the same problem. The variable size cannot be lower
than zero, because it is an unsigned type.

Gary Thomas schrieb:
> 
> A fix for this problem has already been installed.
> 
> We suggest that you use CVS to keep track of the [very] latest
> eCos sources.  See our web page ( http://sourceware.cygnus.com/ecos )
> for the details.
> 
> On 28-Jan-00 Alexander Hering wrote:
> > Hello,
> >
> > we have found an error in the tty driver.
> > When i press the backspace key, when no more characters are in the
> > buffer, the last input is printed again.
> >
> > In function tty_read size is declared as unsigned int, and must not be
> > tested against a value below zero.
> >
> > ====> cyg_uint32 size, clen;
> >
> >       if ((c == '\b') || (c == 0x7F)) {
> >         size -= 2;  // erase one character + 'backspace' char
> > ====>   if (size < 0) size = 0;
> >
> > Greetings
> >
> >       Alex
> >
> > --
> > Fraunhofer-Einrichtung
> >               Systeme der Kommunikationstechnik
> >
> > Alexander Hering              Hansastraße 32
> > Dipl.-Ing.                    D-80686 München
> >                               Telefon: +49(0)89/547088-37
> > E-Mail: Hering@esk.fhg.de     Telefax: +49(0)89/547088-25

-- 
Fraunhofer-Einrichtung
		Systeme der Kommunikationstechnik

Alexander Hering		Hansastraße 32
Dipl.-Ing.			D-80686 München
				Telefon: +49(0)89/547088-37
E-Mail: Hering@esk.fhg.de	Telefax: +49(0)89/547088-25
begin:vcard 
n:Hering;Alexander
tel;fax:+49(0)89/547088-20
tel;work:+49(0)89/547088-37
x-mozilla-html:TRUE
org:Fraunhofer-Einrichtung Systeme der Kommunikationstechnik (ESK)
adr:;;Hansastraße 32/IV;München;Bayern;D-80686;Deutschland (Germany)
version:2.1
email;internet:Hering@esk.fhg.de
title:FhG - ESK
x-mozilla-cpt:;-31232
fn:Hering, Alexander
end:vcard

Re: [ECOS] Error in io\serial\current\src\common\tty.c

[Gary Thomas]

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On 28-Jan-00 Alexander Hering wrote:
> 
> This is a copy of the actual version in CVS:
> 
>     cyg_uint32 size, clen;
> 
>     if ((c == '\b') || (c == 0x7F)) {
>     size -= 2;  // erase one character + 'backspace' char
> ==> if (size < 0) {
>        size = 0;
>     } else if (priv->dev_info.tty_in_flags & CYG_TTY_IN_FLAGS_ECHO) {
>        clen = 3;
>        cyg_io_write(chan, "\b \b", &clen);
>    }
> 
> There is still the same problem. The variable size cannot be lower
> than zero, because it is an unsigned type.
> 

Good catch.  Use this patch to fix it.

Index: io/serial/current//src/common/tty.c
===================================================================
RCS file: /local/cvsfiles/ecc/ecc/io/serial/current/src/common/tty.c,v
retrieving revision 1.8
diff -u -5 -p -r1.8 tty.c
--- io/serial/current//src/common/tty.c 2000/01/28 03:54:54     1.8
+++ io/serial/current//src/common/tty.c 2000/01/28 15:29:15
@@ -191,11 +191,12 @@ static Cyg_ErrNo 
 tty_read(cyg_io_handle_t handle, void *_buf, cyg_uint32 *len)
 {
     cyg_devtab_entry_t *t = (cyg_devtab_entry_t *)handle;
     struct tty_private_info *priv = (struct tty_private_info *)t->priv;
     cyg_io_handle_t chan = (cyg_io_handle_t)priv->dev_handle;
-    cyg_uint32 size, clen;
+    cyg_uint32 clen;
+    cyg_int32 size;
     Cyg_ErrNo res;
     cyg_uint8 c;
     cyg_uint8 *buf = (cyg_uint8 *)_buf;
     // assert(chan)
     size = 0;


> Gary Thomas schrieb:
>> 
>> A fix for this problem has already been installed.
>> 
>> We suggest that you use CVS to keep track of the [very] latest
>> eCos sources.  See our web page ( http://sourceware.cygnus.com/ecos )
>> for the details.
>> 
>> On 28-Jan-00 Alexander Hering wrote:
>> > Hello,
>> >
>> > we have found an error in the tty driver.
>> > When i press the backspace key, when no more characters are in the
>> > buffer, the last input is printed again.
>> >
>> > In function tty_read size is declared as unsigned int, and must not be
>> > tested against a value below zero.
>> >
>> > ====> cyg_uint32 size, clen;
>> >
>> >       if ((c == '\b') || (c == 0x7F)) {
>> >         size -= 2;  // erase one character + 'backspace' char
>> > ====>   if (size < 0) size = 0;
>> >
>> > Greetings
>> >
>> >       Alex
>> >
>> > --
>> > Fraunhofer-Einrichtung
>> >               Systeme der Kommunikationstechnik
>> >
>> > Alexander Hering              Hansastraße 32
>> > Dipl.-Ing.                    D-80686 München
>> >                               Telefon: +49(0)89/547088-37
>> > E-Mail: Hering@esk.fhg.de     Telefax: +49(0)89/547088-25
> 
> -- 
> Fraunhofer-Einrichtung
>               Systeme der Kommunikationstechnik
> 
> Alexander Hering              Hansastraße 32
> Dipl.-Ing.                    D-80686 München
>                               Telefon: +49(0)89/547088-37
> E-Mail: Hering@esk.fhg.de     Telefax: +49(0)89/547088-25