Описание
In the Linux kernel, the following vulnerability has been resolved:
namespace: don't let a pseudo dentry become the root of a mount
d_alloc_pseudo() hands out dentries for pipes, sockets and other files
that are never anyone's child or parent. They carry DCACHE_NORCU and
dentry_free() frees them right away because no lockless path walk can
ever reach them. That holds as long as such a dentry isn't the root of
a mount. But bind mounting /proc/self/fd/ of such a file does
exactly that.
Most callers of alloc_file_pseudo() put their files on kernel-internal
mounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It
places the token file on the bpffs mount the caller handed it and that
mount is in the caller's mount namespace so the clone goes through:
mount --bind /proc/self/fd/
open_tree(tokfd, "", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount()
__follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq
and d_flags of the dentry and only then checks mount_lock. The dentry
can be gone by then. The final mntput() of an unmounted parent unhooks
a child that stayed attached to it under mount_lock alone. When the
child's holder does the final put right after that the root is dput()
and freed immediately while a walker that found the mount hashed still
looks at it.
Refuse to clone a mount with a DCACHE_NORCU dentry as its root. Nothing
sensible can be done with a bind mount of a bpf token anyway.
A flaw was found in the Linux kernel. A local user could exploit a use-after-free vulnerability to cause a Denial of Service (DoS) or potentially escalate privileges on the system. By bind-mounting a pseudo file descriptor, such as a Berkeley Packet Filter (BPF) token, as the root of a mount point, the kernel bypasses normal memory reclamation delays when releasing directory entries. Consequently, concurrent path lookup operations can access freed memory, resulting in memory corruption and a system crash.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Fix deferred |
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Дополнительная информация
Статус:
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: namespace: don't let a pseudo dentry become the root of a mount d_alloc_pseudo() hands out dentries for pipes, sockets and other files that are never anyone's child or parent. They carry DCACHE_NORCU and dentry_free() frees them right away because no lockless path walk can ever reach them. That holds as long as such a dentry isn't the root of a mount. But bind mounting /proc/self/fd/<fd> of such a file does exactly that. Most callers of alloc_file_pseudo() put their files on kernel-internal mounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It places the token file on the bpffs mount the caller handed it and that mount is in the caller's mount namespace so the clone goes through: mount --bind /proc/self/fd/<token> <file> open_tree(tokfd, "", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount() __follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq and d_flags of the dentry and only then ...
In the Linux kernel, the following vulnerability has been resolved: namespace: don't let a pseudo dentry become the root of a mount d_alloc_pseudo() hands out dentries for pipes, sockets and other files that are never anyone's child or parent. They carry DCACHE_NORCU and dentry_free() frees them right away because no lockless path walk can ever reach them. That holds as long as such a dentry isn't the root of a mount. But bind mounting /proc/self/fd/<fd> of such a file does exactly that. Most callers of alloc_file_pseudo() put their files on kernel-internal mounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It places the token file on the bpffs mount the caller handed it and that mount is in the caller's mount namespace so the clone goes through: mount --bind /proc/self/fd/<token> <file> open_tree(tokfd, "", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount() __follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq and d_flags of the dentry and only
In the Linux kernel, the following vulnerability has been resolved: n ...
In the Linux kernel, the following vulnerability has been resolved: namespace: don't let a pseudo dentry become the root of a mount d_alloc_pseudo() hands out dentries for pipes, sockets and other files that are never anyone's child or parent. They carry DCACHE_NORCU and dentry_free() frees them right away because no lockless path walk can ever reach them. That holds as long as such a dentry isn't the root of a mount. But bind mounting /proc/self/fd/<fd> of such a file does exactly that. Most callers of alloc_file_pseudo() put their files on kernel-internal mounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It places the token file on the bpffs mount the caller handed it and that mount is in the caller's mount namespace so the clone goes through: mount --bind /proc/self/fd/<token> <file> open_tree(tokfd, "", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount() __follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq and d_flags of the dentry and o...
5.5 Medium
CVSS3