In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
landlock: Require LANDLOCK_ACCESS_FS_MAKE_REG for whiteout creation<\/p>\n
Whiteout objects are used in the upper layer of an OverlayFS to
\nindicate that the file with this name does not exist in the unified
\nview, even if it is present in one of the lower layer file systems.<\/p>\n
For the userspace implementations of OverlayFS (fuse-overlayfs),
\nwhiteout objects can be created from userspace as well:<\/p>\n
* mknod(2) with S_IFCHR and makedev(0, 0)
\n* renameat2(2) with RENAME_WHITEOUT,
\n creating the whiteout in the old place of the moved file.<\/p>\n
This commit guards whiteout creation in both of these cases with
\nLANDLOCK_ACCESS_FS_MAKE_REG. Whiteout objects are *not* considered
\ncharacter devices and are not bound to a driver.<\/p>\n
LANDLOCK_ACCESS_FS_MAKE_REG describes the same permission class as a
\nwhiteout object: creating one is the only S_IFCHR creation that the VFS
\nexempts from CAP_MKNOD, so it is as unprivileged as creating a regular
\nfile, while LANDLOCK_ACCESS_FS_MAKE_CHAR and
\nLANDLOCK_ACCESS_FS_MAKE_BLOCK keep meaning the creation of devices that
\nexpose a kernel interface [1].<\/p>\n
For the mknod(2) case, introduce a Landlock erratum. The creation of
\nwhiteout objects through mknod(2) was previously guarded using
\nLANDLOCK_ACCESS_FS_MAKE_CHAR, and it is now guarded using
\nLANDLOCK_ACCESS_FS_MAKE_REG.<\/p>\n
For the renameat2(2) case, fix a bug: Before this commit, renameat2(2)
\nwith RENAME_WHITEOUT would create a directory entry even when all
\nLANDLOCK_ACCESS_FS_MAKE_* rights were denied.<\/p>\n
This does not affect normal renames within layered OverlayFS mounts:
\nWhen doing a regular rename() on a mounted fuse-overlayfs, it is the
\nfuse-overlayfs daemon that exercises renameat2() with RENAME_WHITEOUT,
\nand only the Landlock domain of that daemon is checked there.<\/p>\n
Depends-on: 49c9e09d9610 (“landlock: Fix handling of disconnected directories”)
\nDepends-on: fe72ce6710cb (“landlock: Add errata documentation section”)
\n[mic: Record why LANDLOCK_ACCESS_FS_MAKE_REG is the matching right, and
\nadd link(2) to the user doc]<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
landlock: Require LANDLOCK_ACCESS_FS_MAKE_REG for whiteout creation<\/p>\n
Whiteout objects are used in the upper layer of an OverlayFS t<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-21482","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/21482","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21482"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21482"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21482"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}