Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: dcache: don't put a mountpoint on a dentry that's being removed rmdir(), unlink() and rename() call dont_mount() on the victim and then detach_mounts() with the victim's inode locked. do_lock_mount() takes the inode lock of the mountpoint and checks cant_mount() so a mount can't show up after detach_mounts(). But attach_recursive_mnt() makes a second mountpoint for the root of the source mount so that the mounts already located at the destination can be put on top of it. No inode is locked for that one and d_set_mounted() only refuses a dentry that is unlinked. Between detach_mounts() and d_delete() the victim is still hashed: rmrace: b passed dont_mount() and detach_mounts(), sleeping T2: move_mount(S, /tmp/plcant/x, BENEATH) = 0 errno 0 () T1: rmdir(/tmp/plcant/d/b) = 0 errno 0 109 107 0:61 /d/b//deleted /tmp/plcant/x rw,relatime - tmpfs tmpfs rw 108 109 0:63 / /tmp/plcant/x rw,relatime - tmpfs T rw A bind mount of the directory that's being removed is moved beneath an existing mount while the rmdir() is located between the two calls. The mount ends up on the removed directory and nothing will ever detach it. Check cant_mount() in d_set_mounted() as well. dont_mount() raises the flag under d_lock before detach_mounts() runs so either the mountpoint is set first and detach_mounts() finds the mount or the flag is seen and the mount is refused.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 1064f874abc0d05eeed8993815f584d847b72486 before 5e6bfd9f249f2c74bb63c0f06ad959da3bee0971; affected 1064f874abc0d05eeed8993815f584d847b72486 before 793cb67b0f52d00c67bd0e76bc57455b5c70ebb8; affected 1064f874abc0d05eeed8993815f584d847b72486 before 390ddcea2a8aca411b931a8e2863a80ccca8d2b3; affected 1064f874abc0d05eeed8993815f584d847b72486 before 30a1625022411a387cce9239408ece9955bc9c58; affected 1064f874abc0d05eeed8993815f584d847b72486 before 75f4197f1e11d2eb75c2d6f916a7d4764db621e5; affected 5e6ef5ef6eaf690faad3a7c6c665ebf45d7b6ccf; affected 839d42687dfce0ed0ea2c6bd8d707cc0e276fbe7; affected 808e83e5add13152bd4a88346487de68395c136b; affected 6de9d08a9718ee9c12ba6343c50141c2d633e3dc; affected 4.1.40 before 4.2; affected 4.4.54 before 4.5; affected 4.9.15 before 4.10; affected 4.10.3 before 4.11 |
| Linux / Linux | affected 4.11; unaffected 0 before 4.11; unaffected 6.6.160 through 6.6.*; unaffected 6.12.113 through 6.12.*; unaffected 6.18.57 through 6.18.*; unaffected 7.2.11 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/5e6bfd9f249f2c74bb63c0f06ad959da3bee0971
- https://git.kernel.org/stable/c/793cb67b0f52d00c67bd0e76bc57455b5c70ebb8
- https://git.kernel.org/stable/c/390ddcea2a8aca411b931a8e2863a80ccca8d2b3
- https://git.kernel.org/stable/c/30a1625022411a387cce9239408ece9955bc9c58
- https://git.kernel.org/stable/c/75f4197f1e11d2eb75c2d6f916a7d4764db621e5