CVE-2024-39462

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

clk: bcm: dvp: Assign ->num before accessing ->hws

Commit f316cdff8d67 (clk: Annotate struct clk_hw_onecell_data with __counted_by) annotated the hws member of struct clk_hw_onecell_data with __counted_by, which informs the bounds sanitizer about the number of elements in hws, so that it can warn when hws is accessed out of bounds. As noted in that change, the __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in clk_dvp_probe() due to ->num being assigned after ->hws has been accessed:

UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-bcm2711-dvp.c:59:2 index 0 is out of range for type struct clk_hw *[] __counted_by(num) (aka struct clk_hw *[])

Move the ->num initialization to before the first access of ->hws, which clears up the warning.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

Potential Mitigations

• Mitigation of resource exhaustion attacks requires that the target system either:

• The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

• The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/147.html
• https://cwe.mitre.org/data/definitions/227.html
• https://cwe.mitre.org/data/definitions/492.html

References

• https://git.kernel.org/stable/c/0dc913217fb79096597005bba9ba738e2db5cd02
• https://git.kernel.org/stable/c/9368cdf90f52a68120d039887ccff74ff33b4444
• https://git.kernel.org/stable/c/a1dd92fca0d6b58b55ed0484f75d4205dbb77010
• https://git.kernel.org/stable/c/0dc913217fb79096597005bba9ba738e2db5cd02
• https://git.kernel.org/stable/c/9368cdf90f52a68120d039887ccff74ff33b4444
• https://git.kernel.org/stable/c/a1dd92fca0d6b58b55ed0484f75d4205dbb77010