Referring to the value of errno 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.
Non-Compliant Code Example
If the request to register a signal handler can be honored, the signal() function returns the value of 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.
#include <signal.h>
#include <stdlib.h>
#include <string.h>
typedef void (*pfv)(int);
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 */
}
/* main code loop */
return 0;
}
Compliant Solution
The compliant solution does not reference errno.
#include <signal.h>
#include <stdlib.h>
#include <string.h>
typedef void (*pfv)(int);
void handler(int signum) {
pfv old_handler = signal(signum, handler);
if (old_handler == SIG_ERR) {
/* handle error condition */
}
}
int main(void) {
pfv old_handler = signal(SIGINT, handler);
if (old_handler == SIG_ERR) {
perror("SIGINT handler");
/* handle error condition */
}
/* main code loop */
return 0;
}
Risk Assessment
Rule |
Severity |
Likelihood |
Remediation Cost |
Priority |
Level |
|---|---|---|---|---|---|
ERR32-C |
1 (low) |
1 (unlikely) |
3 (low) |
P3 |
L3 |
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
References
[[ISO/IEC 9899-1999]] Section 7.14.1.1, "The signal function"
ERR31-C. Don't redefine errno 13. Error Handling (ERR) ERR33-C. Only examine the value of errno when it is indicated to be valid by a function's return value