CVE-2024-38635

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

soundwire: cadence: fix invalid PDI offset

For some reason, we add an offset to the PDI, presumably to skip the PDI0 and PDI1 which are reserved for BPT.

This code is however completely wrong and leads to an out-of-bounds access. We were just lucky so far since we used only a couple of PDIs and remained within the PDI array bounds.

A Fixes: tag is not provided since there are no known platforms where the out-of-bounds would be accessed, and the initial code had problems as well.

A follow-up patch completely removes this useless offset.

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/002364b2d594a9afc0385c09e00994c510b1d089
• https://git.kernel.org/stable/c/2ebcaa0e5db9b6044bb487ae1cf41bc601761567
• https://git.kernel.org/stable/c/4e99103f757cdf636c6ee860994a19a346a11785
• https://git.kernel.org/stable/c/7eeef1e935d23db5265233d92395bd5c648a4021
• https://git.kernel.org/stable/c/8ee1b439b1540ae543149b15a2a61b9dff937d91
• https://git.kernel.org/stable/c/902f6d656441a511ac25c6cffce74496db10a078
• https://git.kernel.org/stable/c/fd4bcb991ebaf0d1813d81d9983cfa99f9ef5328
• https://git.kernel.org/stable/c/002364b2d594a9afc0385c09e00994c510b1d089
• https://git.kernel.org/stable/c/2ebcaa0e5db9b6044bb487ae1cf41bc601761567
• https://git.kernel.org/stable/c/4e99103f757cdf636c6ee860994a19a346a11785
• https://git.kernel.org/stable/c/7eeef1e935d23db5265233d92395bd5c648a4021
• https://git.kernel.org/stable/c/8ee1b439b1540ae543149b15a2a61b9dff937d91
• https://git.kernel.org/stable/c/902f6d656441a511ac25c6cffce74496db10a078
• https://git.kernel.org/stable/c/fd4bcb991ebaf0d1813d81d9983cfa99f9ef5328