bin/149936: [patch] wrong handling of decompression utilities in libmagic

[Martin Beran]

>Number:         149936
>Category:       bin
>Synopsis:       [patch] wrong handling of decompression utilities in libmagic
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Aug 24 13:40:02 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Martin Beran
>Release:        FreeBSD 8.0-RELEASE-p2 i386
>Organization:
Trusted Network Solutions, a. s.
>Environment:
System: FreeBSD mb.tns.cz 8.0-RELEASE-p2 FreeBSD 8.0-RELEASE-p2 #11: Thu Jul 29 16:49:38 CEST 2010 root at mb.tns.cz:/usr/obj/usr/src/sys/GENERIC i386

Observed also on FreeBSD 7.1.
>Description:
	Function magic_buffer() from libmagic(3) uses external utilities for
	decompression of compressed files. Data from an input in-memory buffer
	should be passed to the external program via a pipe. Due to an
	incorrect condition, the pipe is not initialized, hence no data are
	passed to the program. Moreover, calling close(2) with an argument
	taken from an unitialized memory location causes closing of two
	indeterministically selected file descriptors. If the descriptor
	intended for reading from the decompression process is closed, the
	libmagic code will be stuck in an endless loop, using 100 % CPU,
	calling select(2) that always fails with EBADF.
>How-To-Repeat:
	Call magic_buffer(m, buf, sz) for m obtained by a prior call of
	magic_open(MAGIC_COMPRESS), with buf containing data compressed by
	bzip2.
>Fix:

	Apply the attached patch in /usr/src, recompile and reinstall
	/usr/src/lib/libmagic:

diff -ru contrib.orig/file/compress.c contrib/file/compress.c
--- contrib.orig/file/compress.c	2009-05-19 00:34:33.000000000 +0200
+++ contrib/file/compress.c	2010-08-24 15:09:11.000000000 +0200
@@ -197,6 +197,7 @@
 			if (selrv == -1) {
 				if (errno == EINTR || errno == EAGAIN)
 					continue;
+				return -1;
 			} else if (selrv == 0 && cnt >= 5) {
 				return 0;
 			} else
@@ -381,7 +382,7 @@
 	(void)fflush(stdout);
 	(void)fflush(stderr);
 
-	if ((fd != -1 && pipe(fdin) == -1) || pipe(fdout) == -1) {
+	if ((fd == -1 && pipe(fdin) == -1) || pipe(fdout) == -1) {
 		file_error(ms, errno, "cannot create pipe");	
 		return NODATA;
 	}
>Release-Note:
>Audit-Trail:
>Unformatted: