CVE-2024-42131— mm: avoid overflows in dirty throttling logic

mm: avoid overflows in dirty throttling logic

In the Linux kernel, the following vulnerability has been resolved: mm: avoid overflows in dirty throttling logic The dirty throttling logic is interspersed with assumptions that dirty limits in PAGE_SIZE units fit into 32-bit (so that various multiplications fit into 64-bits). If limits end up being larger, we will hit overflows, possible divisions by 0 etc. Fix these problems by never allowing so large dirty limits as they have dubious practical value anyway. For dirty_bytes / dirty_background_bytes interfaces we can just refuse to set so large limits. For dirty_ratio / dirty_background_ratio it isn't so simple as the dirty limit is computed from the amount of available memory which can change due to memory hotplug etc. So when converting dirty limits from ratios to numbers of pages, we just don't allow the result to exceed UINT_MAX. This is root-only triggerable problem which occurs when the operator sets dirty limits to >16 TB.

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Linux kernel 安全漏洞

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel 存在安全漏洞，该漏洞源于mm模块中在脏页抑制逻辑中，假设脏页限制在PAGE_SIZE单位下适合32位，如果限制更大，可能会遇到溢出和除以零等问题。

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