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zipl/boot: Fix undefined behaviour logic in menu

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The code within 'menu_param()' previously assumed that a read from sclp
will never fail.

If 'sclp_param()' fails then 'endptr' is never initialised and
'loadparm' is compared with 'endptr' which is undefined behvaiour.

If a sclp read fails, an undefined 'endptr' is never accessed, and upon
a failed read, will return a new error code 'SCLP_ERROR' instead of
returning 'NUMBER_FOUND' which is incorrect logic wise.

Remove compare conditions and assignments of 0 in 'value', as 'value'
is initialised with 0 ('DEFAULT_MENU_ENTRY') and cannot be non zero,
only in the case where a number is found and we go to boot.

Logic:

Check if we got a number and boot from it.

If 'PRINT_PROMPT', break out to menu print logic.

If an 'SCLP_ERROR' occurs, print an error message and boot the default
since 'value' is initialised with 'DEFAULT_MENU_ENTRY'.

If 'NOTHING_FOUND', check if the menu is disabled. If disabled, go to
default boot. Otherwise break out to print logic.

Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Richie Buturla <richie@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Richie Buturla
2025-09-09 17:07:00 +02:00
committed by Jan Höppner
parent 4a9f66fc31
commit 20a4ebd83c
1 changed files with 27 additions and 16 deletions
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43
zipl/boot/menu.c
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@@ -102,6 +102,7 @@ enum param_result {
NUMBER_FOUND = 0,
PRINT_PROMPT = 1,
NOTHING_FOUND = 2,
SCLP_ERROR = 3,
};
/*
@@ -114,6 +115,7 @@ enum param_result {
* 0 - found number to boot, stored in value
* 1 - print prompt
* 2 - nothing found
* 3 - sclp error
*/
static enum param_result menu_param(unsigned long *value)
{
@@ -121,8 +123,12 @@ static enum param_result menu_param(unsigned long *value)
char *endptr;
int i;
if (!sclp_param(loadparm))
*value = ebcdic_strtoul(loadparm, &endptr, 10);
/* try to fetch loadparms from sclp into 'loadparm' */
if (sclp_param(loadparm) != 0)
return SCLP_ERROR;
/* parse number from loadparm */
*value = ebcdic_strtoul(loadparm, &endptr, 10);
/* got number, done */
if (endptr != loadparm)
@@ -134,39 +140,44 @@ static enum param_result menu_param(unsigned long *value)
while ((i < PARAM_SIZE) && ecbdic_isspace(loadparm[i]))
i++;
if (!strncmp(&loadparm[i], "PROMPT", 6)) {
*value = 0;
if (!strncmp(&loadparm[i], "PROMPT", 6))
return PRINT_PROMPT;
}
return NOTHING_FOUND;
}
int menu(void)
{
unsigned long value = 0;
enum { DEFAULT_MENU_ENTRY = 0 };
unsigned long value = DEFAULT_MENU_ENTRY;
char *cmd_line_extra;
char endstring[15];
int rc;
cmd_line_extra = (char *)COMMAND_LINE_EXTRA;
memset(cmd_line_extra, 0, COMMAND_LINE_EXTRA_SIZE);
rc = sclp_setup(SCLP_INIT);
if (rc)
if (sclp_setup(SCLP_INIT) != 0) {
/* sclp setup failed boot default */
goto boot;
}
rc = menu_param(&value);
if (rc == NUMBER_FOUND) {
switch (menu_param(&value)) {
case NUMBER_FOUND:
/* got number from loadparm, boot it */
goto boot;
} else if (rc == PRINT_PROMPT && value == 0) {
/* keyword "prompt", show menu */
} else if (__stage2_params.flag == 0) {
/* menu disabled, boot default */
value = 0;
case PRINT_PROMPT:
/* print menu */
break;
case SCLP_ERROR:
/* failed to read from sclp, boot default */
printf("SCLP_ERROR\n");
goto boot;
case NOTHING_FOUND:
if (__stage2_params.flag == 0) {
/* menu disabled, boot default */
goto boot;
}
break;
}
/* print banner */