CVE-2021-47218: selinux: fix NULL-pointer dereference when hashtab allocation fails

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-10 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: selinux: fix NULL-pointer dereference when hashtab allocation fails When the hash table slot array allocation fails in hashtab_init(), h->size is left initialized with a non-zero value, but the h->htable pointer is NULL. This may then cause a NULL pointer dereference, since the policydb code relies on the assumption that even after a failed hashtab_init(), hashtab_map() and hashtab_destroy() can be safely called on it. Yet, these detect an empty hashtab only by looking at the size. Fix this by making sure that hashtab_init() always leaves behind a valid empty hashtab when the allocation fails.

Affected products

Linux kernel: from 5.8 before 5.10.82; from 5.11 before 5.15.5; 5.16-rc1, 5.16-rc2 — fixed in 5.10.82, 5.15.5

How to fix

Upgrade to a fixed version: Linux kernel 5.10.82, 5.15.5. Check the vendor advisory for mitigations.

References

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