Bug 297717

Summary:	sys-apps/util-linux: pg command enters infinite loop
Product:	Gentoo Linux	Reporter:	Mark Calderbank <m.calderbank>
Component:	[OLD] Core system	Assignee:	Gentoo's Team for Core System packages <base-system>
Status:	RESOLVED UPSTREAM
Severity:	normal
Priority:	High
Version:	unspecified
Hardware:	All
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---
Attachments:	Proposed patch

Description Mark Calderbank 2009-12-20 23:46:05 UTC

In a multibyte locale such as en_GB.UTF-8, the pg command cannot handle files containing a form feed character (ASCII 0x0c) at the start of a line. The program enters an infinite loop.

I've traced the problem to the function endline_for_mb in file pg.c. The code assumes that the libc function wcwidth will return a nonnegative value, which is not true for a form feed character. wcwidth returns -1 and the unsigned variable "pos" goes into underflow.

I'll attach a patch which tests whether the character is printable before calling wcwidth. If not, it uses instead the width of the constant L'?' which is later used to replace nonprintable characters. I trust that we can assume printability of this constant :-)

The patch is against the latest release from kernel.org but it looks like the code hasn't changed since the last version in Gentoo.

Reproducible: Always

Steps to Reproduce:
1. Select a multibyte locale (tested with en_GB.UTF-8)
2. Create a file with a form feed character (0x0c) at the start of a line.
3. Try to display this file using the pg command.


Actual Results:  
pg command hangs.

Expected Results:  
pg command should display the file :-)

Comment 1 Mark Calderbank 2009-12-20 23:46:56 UTC

Created attachment 213620 [details, diff]
Proposed patch

Comment 2 SpanKY gentoo-dev

2010-01-05 00:07:42 UTC

upstream has taken your patch ... unless this is a critical issue for you, i'd prefer to just wait for the next release ;)

Comment 3 Mark Calderbank 2010-01-05 13:24:59 UTC

Thanks - next release is fine. I actually used pg by accident, thinking I was on a different Unix box that doesn't have less installed :-)