CVE-2022-50490

In the Linux kernel, the following vulnerability has been resolved:

bpf: Propagate error from htab_lock_bucket() to userspace

In __htab_map_lookup_and_delete_batch() if htab_lock_bucket() returns -EBUSY, it will go to next bucket. Going to next bucket may not only skip the elements in current bucket silently, but also incur out-of-bound memory access or expose kernel memory to userspace if current bucket_cnt is greater than bucket_size or zero.

Fixing it by stopping batch operation and returning -EBUSY when htab_lock_bucket() fails, and the application can retry or skip the busy batch as needed.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/0e13425104903970a5ede853082d3bbb4edec6f3
• https://git.kernel.org/stable/c/4f1f39a8f1ce1b24fee6852d7dcd704ce7c4334d
• https://git.kernel.org/stable/c/66a7a92e4d0d091e79148a4c6ec15d1da65f4280
• https://git.kernel.org/stable/c/6bfee6eb3d6b96ae730a542909dd22b5f9f50d58