CVE-2022-49031

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

iio: health: afe4403: Fix oob read in afe4403_read_raw

KASAN report out-of-bounds read as follows:

BUG: KASAN: global-out-of-bounds in afe4403_read_raw+0x42e/0x4c0 Read of size 4 at addr ffffffffc02ac638 by task cat/279

Call Trace: afe4403_read_raw iio_read_channel_info dev_attr_show

The buggy address belongs to the variable: afe4403_channel_leds+0x18/0xffffffffffffe9e0

This issue can be reproduced by singe command:

$ cat /sys/bus/spi/devices/spi0.0/iio:device0/in_intensity6_raw

The array size of afe4403_channel_leds is less than channels, so access with chan->address cause OOB read in afe4403_read_raw. Fix it by moving access before use it.

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/06c6ce21cec77dfa860d57e7a006000a57812efb
• https://git.kernel.org/stable/c/2d6a437064ffbe685c67ddb16dfc0946074c6c3f
• https://git.kernel.org/stable/c/58143c1ed5882c138a3cd2251a336fc8755f23d9
• https://git.kernel.org/stable/c/726fa3e4ab97dcff1c745bdc4fb137366cb8d3df
• https://git.kernel.org/stable/c/98afcb5f3be645d330c74c5194ba0d80e26f95e0
• https://git.kernel.org/stable/c/b1756af172fb80a3edc143772d49e166ec691b6c
• https://git.kernel.org/stable/c/c9268df36818ee4eaaaeadc80009b442a5ca69c9
• https://git.kernel.org/stable/c/e7e76a77aabef8989cbc0a8417af1aa040620867