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

ibmvnic: Use kernel helpers for hex dumps

Previously, when the driver was printing hex dumps, the buffer was cast to an 8 byte long and printed using string formatters. If the buffer size was not a multiple of 8 then a read buffer overflow was possible.

Therefore, create a new ibmvnic function that loops over a buffer and calls hex_dump_to_buffer instead.

This patch address KASAN reports like the one below: ibmvnic 30000003 env3: Login Buffer: ibmvnic 30000003 env3: 01000000af000000 <…> ibmvnic 30000003 env3: 2e6d62692e736261 ibmvnic 30000003 env3: 65050003006d6f63

BUG: KASAN: slab-out-of-bounds in ibmvnic_login+0xacc/0xffc [ibmvnic] Read of size 8 at addr c0000001331a9aa8 by task ip/17681 <…> Allocated by task 17681: <…> ibmvnic_login+0x2f0/0xffc [ibmvnic] ibmvnic_open+0x148/0x308 [ibmvnic] __dev_open+0x1ac/0x304 <…> The buggy address is located 168 bytes inside of allocated 175-byte region [c0000001331a9a00, c0000001331a9aaf) <…>

ibmvnic 30000003 env3: 000000000033766e

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/ae6b1d6c1acee3a2000394d83ec9f1028321e207
• https://git.kernel.org/stable/c/d93a6caab5d7d9b5ce034d75b1e1e993338e3852