Vulnerability Information
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Vulnerability Title
N/A
Vulnerability Description
The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd_mkdirty() in the touch_pmd() function inside the THP implementation. touch_pmd() can be reached by get_user_pages(). In such case, the pmd will become dirty. This scenario breaks the new can_follow_write_pmd()'s logic - pmd can become dirty without going through a COW cycle. This bug is not as severe as the original "Dirty cow" because an ext4 file (or any other regular file) cannot be mapped using THP. Nevertheless, it does allow us to overwrite read-only huge pages. For example, the zero huge page and sealed shmem files can be overwritten (since their mapping can be populated using THP). Note that after the first write page-fault to the zero page, it will be replaced with a new fresh (and zeroed) thp.
CVSS Information
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Vulnerability Type
N/A
Vulnerability Title
Linux Kernel 安全漏洞
Vulnerability Description
Linux kernel是美国Linux基金会发布的开源操作系统Linux所使用的内核。 Linux Kernel 2.6.38版本至4.14版本中的THP实现的‘touch_pmd()’函数存在安全漏洞，该漏洞源于程序没有正确的使用‘pmd_mkdirty()’函数。攻击者可利用该漏洞覆盖只读权限的大页。
CVSS Information
N/A
Vulnerability Type
N/A