Subject: Bug#547902: dash only reads the first character from pipe (bash reads whole line)

From: Christian Hohnstaedt <[email-masked]>
Date: Thu, 19 Nov 2009 09:27:47 +0100

On Wed, Nov 18, 2009 at 10:13:48PM +0100, Moritz Muehlenhoff wrote:
> On Tue, Oct 13, 2009 at 11:13:01AM +0000, Gerrit Pape wrote:
> > tags 547902 + patch
> > quit
> 
> [ Adding Christian to CC: ]
> 
> Christian, did you submit your patch upstream?

No, not yet.

It still has the problem that reading the value(s) bytewise returns garbage
if the value(s) change during reading.

But I can try to send it to lkml and see what they say.
Shall I point to this bug-report and may I add a "Tested-by" line ?

	Christian

> 
> Cheers,
>         Moritz
> 
> > Hi, please see http://bugs.debian.org/547902
> > 
> > Here's a patch from Christian Hohnstaedt <[email-masked]>
> > 
> > Thanks, Gerrit.
> >
> > 
> > ---
> > Testparameter:
> > for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19; do dd if=/proc/sys/net/ipv4/tcp_wmem bs=$i 2>/dev/null; done
> > 
> > for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19; do dd if=/proc/sys/net/ipv4/tcp_wmem skip=$i bs=1 2>/dev/null |wc -c ; done
> > 
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 9270125..038df14 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -2117,17 +2117,16 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
> >  #define TMPBUFLEN 21
> >  	int *i, vleft, first=1, neg, val;
> >  	unsigned long lval;
> > -	size_t left, len;
> > +	size_t left, len, off;
> >  	
> >  	char buf[TMPBUFLEN], *p;
> >  	char __user *s = buffer;
> >  	
> > -	if (!tbl_data || !table->maxlen || !*lenp ||
> > -	    (*ppos && !write)) {
> > +	if (!tbl_data || !table->maxlen || !*lenp) {
> >  		*lenp = 0;
> >  		return 0;
> >  	}
> > -	
> > +	off = 0;
> >  	i = (int *) tbl_data;
> >  	vleft = table->maxlen / sizeof(*i);
> >  	left = *lenp;
> > @@ -2176,25 +2175,31 @@ static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
> >  			if (conv(&neg, &lval, i, 1, data))
> >  				break;
> >  		} else {
> > +			loff_t diff;
> >  			p = buf;
> > -			if (!first)
> > -				*p++ = '\t';
> > -	
> >  			if (conv(&neg, &lval, i, 0, data))
> >  				break;
> >  
> > -			sprintf(p, "%s%lu", neg ? "-" : "", lval);
> > -			len = strlen(buf);
> > -			if (len > left)
> > -				len = left;
> > -			if(copy_to_user(s, buf, len))
> > -				return -EFAULT;
> > -			left -= len;
> > -			s += len;
> > +			len = sprintf(p, "%s%s%lu", first ? "" : "\t",
> > +						neg ? "-" : "", lval);
> > +			diff = *ppos - off;
> > +			off += len;
> > +			if (diff > 0 && diff < len) {
> > +				p += diff;
> > +				len -= diff;
> > +			}
> > +			if (off > *ppos) {
> > +				if (len > left)
> > +					len = left;
> > +				if(copy_to_user(s, p, len))
> > +					return -EFAULT;
> > +				left -= len;
> > +				s += len;
> > +			}
> >  		}
> >  	}
> >  
> > -	if (!write && !first && left) {
> > +	if (!write && !first && left && off >= *ppos) {
> >  		if(put_user('\n', s))
> >  			return -EFAULT;
> >  		left--, s++;
> > 
> > 
> > 
Christian Hohnstaedt

-- 
Christian Hohnstaedt / Project Manager Hardware and Manufacturing

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