c06391be0 — BusyBox

Subject

Avoid stack munching stdio implementations. -Erik

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

modutils/modprobe.c +100 -75

modutils/modprobe.c+100 -75

@@ -9,13 +9,13 @@
	*/

	#include <sys/utsname.h>
-	#include <stdio.h>
	#include <getopt.h>
	#include <stdlib.h>
	#include <unistd.h>
	#include <syslog.h>
	#include <string.h>
	#include <ctype.h>
+	#include <fcntl.h>
	#include "busybox.h"


@@ -46,11 +46,11 @@ static int autoclean, show_only, quiet, do_syslog, verbose;

	static struct dep_t *build_dep ( void )
	{
+	int fd, n;
	struct utsname un;
-	FILE *f;
	struct dep_t *first = 0;
	struct dep_t *current = 0;
-	char buffer [4096];
+	char buffer[256];
	char *filename = buffer;
	int continuation_line = 0;

@@ -58,21 +58,35 @@ static struct dep_t *build_dep ( void )
	return 0;

	// check for buffer overflow in following code
-	if ( xstrlen ( un. release ) > ( sizeof( buffer ) - 64 ))
+	if ( xstrlen ( un.release ) > ( sizeof( buffer ) - 64 )) {
	return 0;
+	}

	strcpy ( filename, "/lib/modules/" );
-	strcat ( filename, un. release );
+	strcat ( filename, un.release );
	strcat ( filename, "/modules.dep" );

-	f = fopen ( filename, "r" );
-	if ( !f )
+	if ((fd = open ( filename, O_RDONLY )) < 0)
	return 0;
-
-	while ( fgets ( buffer, sizeof( buffer), f )) {
-	int l = xstrlen ( buffer );
+
+	while ( (n = read(fd, buffer, 255)) > 0) {
+	int l;
	char *p = 0;
-
+
+	/* Jump through hoops to simulate how fgets() grabs just one line at a
+	* time... Don't use any stdio since modprobe gets called from a kernel
+	* thread and stdio junk can overflow the limited stack... */
+	p = strchr ( buffer, '\n' );
+	if (p) {
+	off_t offset;
+	/* Get the current file descriptor offset */
+	offset = lseek(fd, 0L, SEEK_CUR);
+	/* Set the file descriptor offset to right after the \n */
+	lseek(fd, offset-n+p-buffer+1, SEEK_SET);
+	*(p+1)='\0';
+	}
+
+	l = xstrlen ( buffer );
	while ( isspace ( buffer [l-1] )) {
	buffer [l-1] = 0;
	l--;
@@ -105,10 +119,10 @@ static struct dep_t *build_dep ( void )
	mod = xstrndup ( mods, col - mods - ext );

	if ( !current ) {
-	first = current = (struct dep_t *) malloc ( sizeof ( struct dep_t ));
+	first = current = (struct dep_t *) xmalloc ( sizeof ( struct dep_t ));
	}
	else {
-	current-> m_next = (struct dep_t *) malloc ( sizeof ( struct dep_t ));
+	current-> m_next = (struct dep_t *) xmalloc ( sizeof ( struct dep_t ));
	current = current-> m_next;
	}
	current-> m_module = mod;
@@ -164,79 +178,90 @@ static struct dep_t *build_dep ( void )
	else
	continuation_line = 0;
	}
-	fclose ( f );
+	close ( fd );

	// alias parsing is not 100% correct (no correct handling of continuation lines within an alias) !

-	f = fopen ( "/etc/modules.conf", "r" );
-	if ( !f )
-	f = fopen ( "/etc/conf.modules", "r" );
-	if ( f ) {
-	continuation_line = 0;
+	if ((fd = open ( "/etc/modules.conf", O_RDONLY )) < 0)
+	if ((fd = open ( "/etc/conf.modules", O_RDONLY )) < 0)
+	return first;

-	while ( fgets ( buffer, sizeof( buffer), f )) {
-	int l;
-	char *p;
-
-	p = strchr ( buffer, '#' );
-	if ( p )
-	*p = 0;
-
-	l = xstrlen ( buffer );
+	continuation_line = 0;
+	while ( read(fd, buffer, 255) > 0) {
+	int l;
+	char *p;

-	while ( l && isspace ( buffer [l-1] )) {
-	buffer [l-1] = 0;
-	l--;
-	}
-
-	if ( l == 0 ) {
-	continuation_line = 0;
-	continue;
-	}
+	/* Jump through hoops to simulate how fgets() grabs just one line at a
+	* time... Don't use any stdio since modprobe gets called from a kernel
+	* thread and stdio junk can overflow the limited stack... */
+	p = strchr ( buffer, '\n' );
+	if (p) {
+	off_t offset;
+	/* Get the current file descriptor offset */
+	offset = lseek(fd, 0L, SEEK_CUR);
+	/* Set the file descriptor offset to right after the \n */
+	lseek(fd, offset-n+p-buffer+1, SEEK_SET);
+	*(p+1)='\0';
+	}
+
+	p = strchr ( buffer, '#' );
+	if ( p )
+	*p = 0;

-	if ( !continuation_line ) {
-	if (( strncmp ( buffer, "alias", 5 ) == 0 ) && isspace ( buffer [5] )) {
-	char alias, mod;
+	l = xstrlen ( buffer );
+
+	while ( l && isspace ( buffer [l-1] )) {
+	buffer [l-1] = 0;
+	l--;
+	}
+
+	if ( l == 0 ) {
+	continuation_line = 0;
+	continue;
+	}
+
+	if ( !continuation_line ) {
+	if (( strncmp ( buffer, "alias", 5 ) == 0 ) && isspace ( buffer [5] )) {
+	char alias, mod;

-	alias = buffer + 6;
-
-	while ( isspace ( *alias ))
-	alias++;
-	mod = alias;
-	while ( !isspace ( *mod ))
-	mod++;
-	*mod = 0;
+	alias = buffer + 6;
+
+	while ( isspace ( *alias ))
+	alias++;
+	mod = alias;
+	while ( !isspace ( *mod ))
+	mod++;
+	*mod = 0;
+	mod++;
+	while ( isspace ( *mod ))
	mod++;
-	while ( isspace ( *mod ))
-	mod++;
-
+
	// fprintf ( stderr, "ALIAS: '%s' -> '%s'\n", alias, mod );
-
-	if ( !current ) {
-	first = current = (struct dep_t *) malloc ( sizeof ( struct dep_t ));
-	}
-	else {
-	current-> m_next = (struct dep_t *) malloc ( sizeof ( struct dep_t ));
-	current = current-> m_next;
-	}
-	current-> m_module = xstrdup ( alias );
-	current-> m_isalias = 1;
-
-	if (( strcmp ( alias, "off" ) == 0 ) \|\| ( strcmp ( alias, "null" ) == 0 )) {
-	current-> m_depcnt = 0;
-	current-> m_deparr = 0;
-	}
-	else {
-	current-> m_depcnt = 1;
-	current-> m_deparr = xmalloc ( 1 * sizeof( char * ));
-	current-> m_deparr[0] = xstrdup ( mod );
-	}
-	current-> m_next = 0;
-	}
-	}
+
+	if ( !current ) {
+	first = current = (struct dep_t *) xmalloc ( sizeof ( struct dep_t ));
+	}
+	else {
+	current-> m_next = (struct dep_t *) xmalloc ( sizeof ( struct dep_t ));
+	current = current-> m_next;
+	}
+	current-> m_module = xstrdup ( alias );
+	current-> m_isalias = 1;
+
+	if (( strcmp ( alias, "off" ) == 0 ) \|\| ( strcmp ( alias, "null" ) == 0 )) {
+	current-> m_depcnt = 0;
+	current-> m_deparr = 0;
+	}
+	else {
+	current-> m_depcnt = 1;
+	current-> m_deparr = xmalloc ( 1 * sizeof( char * ));
+	current-> m_deparr[0] = xstrdup ( mod );
+	}
+	current-> m_next = 0;
+	}
	}
-	fclose ( f );
	}
+	close ( fd );

	return first;
	}