CVE-2021-47153

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

i2c: i801: Dont generate an interrupt on bus reset

Now that the i2c-i801 driver supports interrupts, setting the KILL bit in a attempt to recover from a timed out transaction triggers an interrupt. Unfortunately, the interrupt handler (i801_isr) is not prepared for this situation and will try to process the interrupt as if it was signaling the end of a successful transaction. In the case of a block transaction, this can result in an out-of-range memory access.

This condition was reproduced several times by syzbot: https://syzkaller.appspot.com/bug?extid=ed71512d469895b5b34e https://syzkaller.appspot.com/bug?extid=8c8dedc0ba9e03f6c79e https://syzkaller.appspot.com/bug?extid=c8ff0b6d6c73d81b610e https://syzkaller.appspot.com/bug?extid=33f6c360821c399d69eb https://syzkaller.appspot.com/bug?extid=be15dc0b1933f04b043a https://syzkaller.appspot.com/bug?extid=b4d3fd1dfd53e90afd79

So disable interrupts while trying to reset the bus. Interrupts will be enabled again for the following transaction.

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/04cc05e3716ae31b17ecdab7bc55c8170def1b8b
• https://git.kernel.org/stable/c/09c9e79f4c10cfb6b9e0e1b4dd355232e4b5a3b3
• https://git.kernel.org/stable/c/1f583d3813f204449037cd2acbfc09168171362a
• https://git.kernel.org/stable/c/b523feb7e8e44652f92f3babb953a976e7ccbbef
• https://git.kernel.org/stable/c/c70e1ba2e7e65255a0ce004f531dd90dada97a8c
• https://git.kernel.org/stable/c/dfa8929e117b0228a7765f5c3f5988a4a028f3c6
• https://git.kernel.org/stable/c/e4d8716c3dcec47f1557024add24e1f3c09eb24b
• https://git.kernel.org/stable/c/f9469082126cebb7337db3992d143f5e4edfe629
• https://git.kernel.org/stable/c/04cc05e3716ae31b17ecdab7bc55c8170def1b8b
• https://git.kernel.org/stable/c/09c9e79f4c10cfb6b9e0e1b4dd355232e4b5a3b3
• https://git.kernel.org/stable/c/1f583d3813f204449037cd2acbfc09168171362a
• https://git.kernel.org/stable/c/b523feb7e8e44652f92f3babb953a976e7ccbbef
• https://git.kernel.org/stable/c/c70e1ba2e7e65255a0ce004f531dd90dada97a8c
• https://git.kernel.org/stable/c/dfa8929e117b0228a7765f5c3f5988a4a028f3c6
• https://git.kernel.org/stable/c/e4d8716c3dcec47f1557024add24e1f3c09eb24b
• https://git.kernel.org/stable/c/f9469082126cebb7337db3992d143f5e4edfe629