CVE-2022-49515

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

ASoC: cs35l41: Fix an out-of-bounds access in otp_packed_element_t

The CS35L41_NUM_OTP_ELEM is 100, but only 99 entries are defined in the array otp_map_1/2[CS35L41_NUM_OTP_ELEM], this will trigger UBSAN to report a shift-out-of-bounds warning in the cs35l41_otp_unpack() since the last entry in the array will result in GENMASK(-1, 0).

UBSAN reports this problem: UBSAN: shift-out-of-bounds in /home/hwang4/build/jammy/jammy/sound/soc/codecs/cs35l41-lib.c:836:8 shift exponent 64 is too large for 64-bit type long unsigned int CPU: 10 PID: 595 Comm: systemd-udevd Not tainted 5.15.0-23-generic #23 Hardware name: LENOVO x02MFG_IN_GO/x02MFG_IN_GO, BIOS N3GET19W (1.00 ) 03/11/2022 Call Trace: show_stack+0x52/0x58 dump_stack_lvl+0x4a/0x5f dump_stack+0x10/0x12 ubsan_epilogue+0x9/0x45 __ubsan_handle_shift_out_of_bounds.cold+0x61/0xef ? regmap_unlock_mutex+0xe/0x10 cs35l41_otp_unpack.cold+0x1c6/0x2b2 [snd_soc_cs35l41_lib] cs35l41_hda_probe+0x24f/0x33a [snd_hda_scodec_cs35l41] cs35l41_hda_i2c_probe+0x65/0x90 [snd_hda_scodec_cs35l41_i2c] ? cs35l41_hda_i2c_remove+0x20/0x20 [snd_hda_scodec_cs35l41_i2c] i2c_device_probe+0x252/0x2b0

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/9f342904216f378e88008bb0ce1ae200a4b99fe8
• https://git.kernel.org/stable/c/a59b9958416096dd21dc4f62b0c5be525d459ca8
• https://git.kernel.org/stable/c/dbc35268e14d5d89c7a9db72009ad4dcd9ede646