CVE-2022-50094

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

spmi: trace: fix stack-out-of-bound access in SPMI tracing functions

trace_spmi_write_begin() and trace_spmi_read_end() both call memcpy() with a length of len + 1. This leads to one extra byte being read beyond the end of the specified buffer. Fix this out-of-bound memory access by using a length of len instead.

Here is a KASAN log showing the issue:

BUG: KASAN: stack-out-of-bounds in trace_event_raw_event_spmi_read_end+0x1d0/0x234 Read of size 2 at addr ffffffc0265b7540 by task thermal@2.0-ser/1314 … Call trace: dump_backtrace+0x0/0x3e8 show_stack+0x2c/0x3c dump_stack_lvl+0xdc/0x11c print_address_description+0x74/0x384 kasan_report+0x188/0x268 kasan_check_range+0x270/0x2b0 memcpy+0x90/0xe8 trace_event_raw_event_spmi_read_end+0x1d0/0x234 spmi_read_cmd+0x294/0x3ac spmi_ext_register_readl+0x84/0x9c regmap_spmi_ext_read+0x144/0x1b0 [regmap_spmi] _regmap_raw_read+0x40c/0x754 regmap_raw_read+0x3a0/0x514 regmap_bulk_read+0x418/0x494 adc5_gen3_poll_wait_hs+0xe8/0x1e0 [qcom_spmi_adc5_gen3] … __arm64_sys_read+0x4c/0x60 invoke_syscall+0x80/0x218 el0_svc_common+0xec/0x1c8 …

addr ffffffc0265b7540 is located in stack of task thermal@2.0-ser/1314 at offset 32 in frame: adc5_gen3_poll_wait_hs+0x0/0x1e0 [qcom_spmi_adc5_gen3]

this frame has 1 object: [32, 33) status

Memory state around the buggy address: ffffffc0265b7400: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 ffffffc0265b7480: 04 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00

ffffffc0265b7500: 00 00 00 00 f1 f1 f1 f1 01 f3 f3 f3 00 00 00 00 ^ ffffffc0265b7580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffffffc0265b7600: f1 f1 f1 f1 01 f2 07 f2 f2 f2 01 f3 00 00 00 00 ==================================================================

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/1e0ca3d809c36ad3d1f542917718fc22ec6316e7
• https://git.kernel.org/stable/c/2af28b241eea816e6f7668d1954f15894b45d7e3
• https://git.kernel.org/stable/c/37690cb8662cec672cacda19e6e4fd2ca7b13f0b
• https://git.kernel.org/stable/c/504090815c1ad3fd3fa34618b54d706727f8911c
• https://git.kernel.org/stable/c/80f7c93e573ea9f524924bb529c2af8cb28b1c43
• https://git.kernel.org/stable/c/ac730c72bddc889f5610d51d8a7abf425e08da1a
• https://git.kernel.org/stable/c/bcc1b6b1ed3f42ed25858c1f1eb24a2f741db93f
• https://git.kernel.org/stable/c/dc6033a7761254e5a5ba7df36b64db787a53313c
• https://git.kernel.org/stable/c/dd02510fb43168310abfd0b9ccf49993a722fb91