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38. Writing Secure Privileged Programs > Beware of Signals and Race Conditions

Beware of Signals and Race Conditions

A user may send arbitrary signals to a set-user-ID program that they have started. Such signals may arrive at any time and with any frequency. We need to consider the race conditions that can occur if a signal is delivered at any point in the execution of the program. Where appropriate, signals should be caught, blocked, or ignored to prevent possible security problems. Furthermore, the design of signal handlers should be as simple as possible, in order to reduce the risk of inadvertently creating a race condition.

This issue is particularly relevant with the signals that stop a process (e.g., SIGTSTP and SIGSTOP). The problematic scenario is the following:


  

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