module
2021 Ubuntu Overlayfs LPE
Disclosed | Created |
---|---|
Apr 12, 2021 | Dec 8, 2021 |
Disclosed
Apr 12, 2021
Created
Dec 8, 2021
Description
This module exploits a vulnerability in Ubuntu's implementation of overlayfs. The
vulnerability is the result of failing to verify the ability of a user to set the
attributes in a running executable. Specifically, when Overlayfs sends the set attributes
data to the underlying file system via `vfs_setxattr`, it fails to first verify the data
by calling `cap_convert_nscap`.
This vulnerability was patched by moving the call to `cap_convert_nscap`
into the `vfs_setxattr` function that sets the attribute, forcing verification every time the
`vfs_setxattr` is called rather than trusting the data was already verified.
vulnerability is the result of failing to verify the ability of a user to set the
attributes in a running executable. Specifically, when Overlayfs sends the set attributes
data to the underlying file system via `vfs_setxattr`, it fails to first verify the data
by calling `cap_convert_nscap`.
This vulnerability was patched by moving the call to `cap_convert_nscap`
into the `vfs_setxattr` function that sets the attribute, forcing verification every time the
`vfs_setxattr` is called rather than trusting the data was already verified.
Authors
ssd-disclosure
bwatters-r7
bwatters-r7
Platform
Linux
References
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