Affected: Alpaquita:23: linux-lts, Alpaquita:25: linux-lts, Alpaquita:stream: linux-lts

In the Linux kernel, the following vulnerability has been resolved:

ocfs2/dlm: require a ref for locking_state debugfs open

debug_lockres_open() copies inode->i_private into struct debug_lockres and debug_lockres_release() later drops that pointer with dlm_put(). That only works if open successfully pins the struct dlm_ctxt.

Today open calls dlm_grab(dlm) but ignores its return value. Once the last domain unregister has removed the context from dlm_domains, dlm_grab() returns NULL, yet open still stores the raw pointer and returns success. The later release path is outside the debugfs removal barrier, so it can call dlm_put() after dlm_free_ctxt_mem() has freed the context. KASAN reports this as a slab-use-after-free in dlm_put() called from debug_lockres_release().

Fail the open when dlm_grab() cannot acquire the reference and unwind the seq_file private state before returning. That keeps locking_state from handing out a file descriptor whose release path does not own the dlm_ctxt.

The buggy scenario involves two paths, with each column showing the order within that path:

locking_state debugfs open: last domain unregister: 1. debug_lockres_open() reads 1. dlm_unregister_domain() calls inode->i_private. dlm_complete_dlm_shutdown(). 2. debug_lockres_open() calls 2. shutdown removes the dlm_ctxt from dlm_grab(dlm) and gets NULL. dlm_domains. 3. open still stores the raw dlm 3. final teardown reaches poin…

In the Linux kernel, the following vulnerability has been resolved:

ocfs2/dlm: require a ref for locking_state debugfs open

debug_lockres_open() copies inode->i_private into struct debug_lockres and debug_lockres_release() later drops that pointer with dlm_put(). That only works if open successfully pins the struct dlm_ctxt.

Today open calls dlm_grab(dlm) but ignores its return value. Once the last domain unregister has removed the context from dlm_domains, dlm_grab() returns NULL, yet open still stores the raw pointer and returns success. The later release path is outside the debugfs removal barrier, so it can call dlm_put() after dlm_free_ctxt_mem() has freed the context. KASAN reports this as a slab-use-after-free in dlm_put() called from debug_lockres_release().

Fail the open when dlm_grab() cannot acquire the reference and unwind the seq_file private state before returning. That keeps locking_state from handing out a file descriptor whose release path does not own the dlm_ctxt.

The buggy scenario involves two paths, with each column showing the order within that path:

locking_state debugfs open: last domain unregister: 1. debug_lockres_open() reads 1. dlm_unregister_domain() calls inode->i_private. dlm_complete_dlm_shutdown(). 2. debug_lockres_open() calls 2. shutdown removes the dlm_ctxt from dlm_grab(dlm) and gets NULL. dlm_domains. 3. open still stores the raw dlm 3. final teardown reaches poin…

Affected: Ubuntu:Pro:14.04:LTS: linux, Ubuntu:Pro:14.04:LTS: linux-aws, Ubuntu:Pro:14.04:LTS: linux-azure, Ubuntu:Pro:14.04:LTS: linux-lts-xenial, Ubuntu:Pro:16.04:LTS: linux, Ubuntu:Pro:16.04:LTS: linux-aws, Ubuntu:Pro:16.04:LTS: linux-aws-hwe, Ubuntu:Pro:16.04:LTS: linux-azure, Ubuntu:Pro:16.04:LTS: linux-gcp, Ubuntu:Pro:16.04:LTS: linux-hwe and 246 more

In the Linux kernel, the following vulnerability has been resolved: ocfs2/dlm: require a ref for locking_state debugfs open debug_lockres_open() copies inode->i_private into struct debug_lockres and debug_lockres_release() later drops that pointer with dlm_put(). That only works if open successfully pins the struct dlm_ctxt. Today open calls dlm_grab(dlm) but ignores its return value. Once the last domain unregister has removed the context from dlm_domains, dlm_grab() returns NULL, yet open still stores the raw pointer and returns success. The later release path is outside the debugfs removal barrier, so it can call dlm_put() after dlm_free_ctxt_mem() has freed the context. KASAN reports this as a slab-use-after-free in dlm_put() called from debug_lockres_release(). Fail the open when dlm_grab() cannot acquire the reference and unwind the seq_file private state before returning. That keeps locking_state from handing out a file descriptor whose release path does not own the dlm_ctxt. The buggy scenario involves two paths, with each column showing the order within that path: locking_state debugfs open: last domain unregister: 1. debug_lockres_open() reads 1. dlm_unregister_domain() calls inode->i_private. dlm_complete_dlm_shutdown(). 2. debug_lockres_open() calls 2. shutdown removes the dlm_ctxt from dlm_grab(dlm) and gets NULL. dlm_domains. 3. open still stores the raw dlm 3. final teardown reaches pointer in…

Ein Angreifer kann mehrere Schwachstellen in Linux Kernel ausnutzen, um root Rechte zu erlangen, um einen Denial of Service herbeizuführen oder einen nicht näher spezifizierten Angriff durchzuführen.