CVE-2024-36916

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

blk-iocost: avoid out of bounds shift

UBSAN catches undefined behavior in blk-iocost, where sometimes iocg->delay is shifted right by a number that is too large, resulting in undefined behavior on some architectures.

[ 186.556576] ————[ cut here ]———— UBSAN: shift-out-of-bounds in block/blk-iocost.c:1366:23 shift exponent 64 is too large for 64-bit type u64 (aka unsigned long long) CPU: 16 PID: 0 Comm: swapper/16 Tainted: G S E N 6.9.0-0_fbk700_debug_rc2_kbuilder_0_gc85af715cac0 #1 Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A23 12/08/2020 Call Trace: dump_stack_lvl+0x8f/0xe0 __ubsan_handle_shift_out_of_bounds+0x22c/0x280 iocg_kick_delay+0x30b/0x310 ioc_timer_fn+0x2fb/0x1f80 __run_timer_base+0x1b6/0x250 …

Avoid that undefined behavior by simply taking the delay = 0 branch if the shift is too large.

I am not sure what the symptoms of an undefined value delay will be, but I suspect it could be more than a little annoying to debug.

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/488dc6808cb8369685f18cee81e88e7052ac153b
• https://git.kernel.org/stable/c/62accf6c1d7b433752cb3591bba8967b7a801ad5
• https://git.kernel.org/stable/c/844fc023e9f14a4fb1de5ae1eaefafd6d69c5fa1
• https://git.kernel.org/stable/c/beaa51b36012fad5a4d3c18b88a617aea7a9b96d
• https://git.kernel.org/stable/c/ce0e99cae00e3131872936713b7f55eefd53ab86
• https://git.kernel.org/stable/c/f6add0a6f78dc6360b822ca4b6f9f2f14174c8ca
• https://git.kernel.org/stable/c/488dc6808cb8369685f18cee81e88e7052ac153b
• https://git.kernel.org/stable/c/62accf6c1d7b433752cb3591bba8967b7a801ad5
• https://git.kernel.org/stable/c/844fc023e9f14a4fb1de5ae1eaefafd6d69c5fa1
• https://git.kernel.org/stable/c/beaa51b36012fad5a4d3c18b88a617aea7a9b96d
• https://git.kernel.org/stable/c/ce0e99cae00e3131872936713b7f55eefd53ab86
• https://git.kernel.org/stable/c/f6add0a6f78dc6360b822ca4b6f9f2f14174c8ca
• https://lists.debian.org/debian-lts-announce/2024/06/msg00019.html
• https://security.netapp.com/advisory/ntap-20240905-0006/