If a call Referring to the signal() function occurs value of errno after a signal occurred other than as the result of calling the abort() or raise() function , and the XXX results in corresponding signal handler obtained a SIG_ERR return from a call to the signal() function.
Non-Compliant Code Example
If the request to register a signal handler can be honored, the signal() function returns the value of errno is indeterminate.The value of errno is referred to after a signal occurred other than as the result of calling the abort() or raise() function and the corresponding signal handler obtained a SIG_ERR return from a call to the signal() function.the signal handler for the most recent successful call to the signal() function for the specified signal. Otherwise, a value of
SIG_ERR is returned and a positive value is stored in errno.
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#include <signal.h>
#include <stdlib.h>
#include <string.h>
char *err_msg;
volatile sig_atomic_t e_flag = 0;
void handler(int signum) {
signal(signum, handler);
e_flag = 1;
}
int main(void) {
signal(SIGINT, handler);
err_msg = (char *)malloc(24);
if (err_msg == NULL) {
/* handle error condition */
}
strcpy(err_msg, "No errors yet.");
/* main code loop */
if (e_flag) {
strcpy(err_msg, "SIGINT received.");
}
return 0;
}
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Compliant Solution
To be safe, signal handlers should only unconditionally set a flag of type volatile sig_atomic_t and return.
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#include <signal.h>
#include <stdlib.h>
#include <string.h>
typedef void (*pfv)(int);
char *err_msg;
void handler(int signum) {
pfv old_handler = signal(signum, handler);
if (old_handler == SIG_ERR) {
perror("SIGINT handler"); /* undefined behavior */
/* handle error condition */
}
strcpy(err_msg, "SIGINT encountered.");
}
int main(void) {
pfv old_handler = signal(SIGINT, handler);
if (old_handler == SIG_ERR) {
perror("SIGINT handler");
/* handle error condition */
}
err_msg = (char *)malloc(24);
if (err_msg == NULL) {
/* handle error condition */
}
strcpy(err_msg, "No errors yet.");
/* main code loop */
return 0;
}
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Risk Assessment
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
ERR32-C | 1 (low) | 1 (unlikely) | 3 (low) | P3 | L3 |
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