Concurrent writes to a map

Description

Writing to a map from multiple goroutines is not concurrency safe. This can lead to a race condition where the map is modified by one goroutine while another goroutine is iterating over it, resulting in unpredictable behavior.

Examples

Insecure Code

var m map[string]int

func main() {
    m = make(map[string]int)
    go func() {
        m["key"] = 1
    }()
    m["key"] = 2
}

Secure Code

var m map[string]int
var mu sync.Mutex

func main() {
    m = make(map[string]int)
    go func() {
        mu.Lock()
        m["key"] = 1
        mu.Unlock()
    }()
    mu.Lock()
    m["key"] = 2
    mu.Unlock()
}

Remediation

Use a mutex to synchronize access to the map, or use a concurrency-safe map implementation.

Rule Details

Field	Value
ID	CODE-0273
Category	Concurrency
Severity	HIGH
CWE	CWE-362
Confidence	MEDIUM
Impact	MEDIUM
Likelihood	HIGH
Exploitability	EASY
Tags	race condition, concurrency
OWASP	N/A

References

• https://go.dev/blog/maps#concurrency

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