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[settings] Avoid returning uninitialised data on error in fetch_xxx_setting() 

Callers (e.g. usr/autoboot.c) may not check the return values from
fetch_xxx_setting(), assuming that in error cases the returned setting
value will be "empty" (for some sensible value of "empty").

In particular, if the DHCP server did not specify a next-server
address, this would result in gPXE using uninitialised data for the
TFTP server IP address.
This commit is contained in:
Michael Brown 2008-10-22 21:18:15 +01:00
parent cbf9003d66
commit 612f4e7a99
1 changed files with 15 additions and 5 deletions
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20
src/core/settings.c
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@ -333,6 +333,9 @@ int fetch_setting ( struct settings *settings, struct setting *setting,
struct settings *child;
int ret;
/* Avoid returning uninitialised data on error */
memset ( data, 0, len );
/* NULL settings implies starting at the global settings root */
if ( ! settings )
settings = &settings_root;
@ -381,7 +384,6 @@ int fetch_setting_len ( struct settings *settings, struct setting *setting ) {
*/
int fetch_string_setting ( struct settings *settings, struct setting *setting,
char *data, size_t len ) {
memset ( data, 0, len );
return fetch_setting ( settings, setting, data,
( ( len > 0 ) ? ( len - 1 ) : 0 ) );
}
@ -417,20 +419,23 @@ int fetch_ipv4_setting ( struct settings *settings, struct setting *setting,
int fetch_int_setting ( struct settings *settings, struct setting *setting,
long *value ) {
union {
long value;
uint8_t u8[ sizeof ( long ) ];
int8_t s8[ sizeof ( long ) ];
} buf;
int len;
int i;
buf.value = 0;
/* Avoid returning uninitialised data on error */
*value = 0;
/* Fetch raw (network-ordered, variable-length) setting */
len = fetch_setting ( settings, setting, &buf, sizeof ( buf ) );
if ( len < 0 )
return len;
if ( len > ( int ) sizeof ( buf ) )
return -ERANGE;
/* Convert to host-ordered signed long */
*value = ( ( buf.s8[0] >= 0 ) ? 0 : -1L );
for ( i = 0 ; i < len ; i++ ) {
*value = ( ( *value << 8 ) | buf.u8[i] );
@ -452,10 +457,15 @@ int fetch_uint_setting ( struct settings *settings, struct setting *setting,
long svalue;
int len;
/* Avoid returning uninitialised data on error */
*value = 0;
/* Fetch as a signed long */
len = fetch_int_setting ( settings, setting, &svalue );
if ( len < 0 )
return len;
/* Mask off sign-extended bits */
*value = ( svalue & ( -1UL >> ( sizeof ( long ) - len ) ) );
return len;
@ -469,7 +479,7 @@ int fetch_uint_setting ( struct settings *settings, struct setting *setting,
* @ret value Setting value, or zero
*/
long fetch_intz_setting ( struct settings *settings, struct setting *setting ){
long value = 0;
long value;
fetch_int_setting ( settings, setting, &value );
return value;
@ -484,7 +494,7 @@ long fetch_intz_setting ( struct settings *settings, struct setting *setting ){
*/
unsigned long fetch_uintz_setting ( struct settings *settings,
struct setting *setting ) {
unsigned long value = 0;
unsigned long value;
fetch_uint_setting ( settings, setting, &value );
return value;