CWE-820: Missing Synchronization
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Edit Custom FilterThe product utilizes a shared resource in a concurrent manner but does not attempt to synchronize access to the resource.
If access to a shared resource is not synchronized, then the resource may not be in a state that is expected by the product. This might lead to unexpected or insecure behaviors, especially if an attacker can influence the shared resource.
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Example 1 The following code intends to fork a process, then have both the parent and child processes print a single line. (bad code)
Example Language: C
static void print (char * string) {
char * word;
int counter; for (word = string; counter = *word++; ) { putc(counter, stdout);
fflush(stdout); /* Make timing window a little larger... */ sleep(1); int main(void) { pid_t pid;
pid = fork(); if (pid == -1) { exit(-2); }else if (pid == 0) { print("child\n"); }else { print("PARENT\n"); }exit(0); One might expect the code to print out something like:
PARENT
child
However, because the parent and child are executing concurrently, and stdout is flushed each time a character is printed, the output might be mixed together, such as:
PcAhRiElNdT
[blank line]
[blank line]
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Maintenance
Deeper research is necessary for synchronization and related mechanisms, including locks, mutexes, semaphores, and other mechanisms. Multiple entries are dependent on this research, which includes relationships to concurrency, race conditions, reentrant functions, etc. CWE-662 and its children - including CWE-667, CWE-820, CWE-821, and others - may need to be modified significantly, along with their relationships.
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