CWE-479: Signal Handler Use of a Non-reentrant Function
Description
The product defines a signal handler that calls a non-reentrant function.
Submission Date :
July 19, 2006, midnight
Modification Date :
2023-10-26 00:00:00+00:00
Organization :
MITRE
Extended Description
Non-reentrant functions are functions that cannot safely be called, interrupted, and then recalled before the first call has finished without resulting in memory corruption. This can lead to an unexpected system state and unpredictable results with a variety of potential consequences depending on context, including denial of service and code execution.
Many functions are not reentrant, but some of them can result in the corruption of memory if they are used in a signal handler. The function call syslog() is an example of this. In order to perform its functionality, it allocates a small amount of memory as "scratch space." If syslog() is suspended by a signal call and the signal handler calls syslog(), the memory used by both of these functions enters an undefined, and possibly, exploitable state. Implementations of malloc() and free() manage metadata in global structures in order to track which memory is allocated versus which memory is available, but they are non-reentrant. Simultaneous calls to these functions can cause corruption of the metadata.
Example - 1
In this example, a signal handler uses syslog() to log a message:
syslog(LOG_NOTICE,"%s\n",message);sleep(10);exit(0);
...signal(SIGHUP,sh);signal(SIGTERM,sh);sleep(10);exit(0);If the execution of the first call to the signal handler is suspended after invoking syslog(), and the signal handler is called a second time, the memory allocated by syslog() enters an undefined, and possibly, exploitable state.char *message;void sh(int dummy) {}int main(int argc,char* argv[]) {}
Related Weaknesses
This table shows the weaknesses and high level categories that are related to this weakness. These relationships are defined to give an overview of the different insight to similar items that may exist at higher and lower levels of abstraction.
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