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

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

tmpfs: fix race on handling dquot rbtree

A syzkaller reproducer found a race while attempting to remove dquot information from the rb tree.

Fetching the rb_tree root node must also be protected by the dqopt->dqio_sem, otherwise, giving the right timing, shmem_release_dquot() will trigger a warning because it couldn't find a node in the tree, when the real reason was the root node changing before the search starts:

Thread 1 Thread 2 - shmem_release_dquot() - shmem_{acquire,release}_dquot()

- fetch ROOT - Fetch ROOT

- acquire dqio_sem - wait dqio_sem

- do something, triger a tree rebalance - release dqio_sem

- acquire dqio_sem - start searching for the node, but from the wrong location, missing the node, and triggering a warning.

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

tmpfs: fix race on handling dquot rbtree

A syzkaller reproducer found a race while attempting to remove dquot information from the rb tree.

Fetching the rb_tree root node must also be protected by the dqopt->dqio_sem, otherwise, giving the right timing, shmem_release_dquot() will trigger a warning because it couldn't find a node in the tree, when the real reason was the root node changing before the search starts:

Thread 1 Thread 2 - shmem_release_dquot() - shmem_{acquire,release}_dquot()

- fetch ROOT - Fetch ROOT

- acquire dqio_sem - wait dqio_sem

- do something, triger a tree rebalance - release dqio_sem

- acquire dqio_sem - start searching for the node, but from the wrong location, missing the node, and triggering a warning.

Affected: Ubuntu:16.04:LTS: linux-hwe-edge, Ubuntu:18.04:LTS: linux-aws-5.0, Ubuntu:18.04:LTS: linux-aws-5.3, Ubuntu:18.04:LTS: linux-azure, Ubuntu:18.04:LTS: linux-azure-5.3, Ubuntu:18.04:LTS: linux-azure-edge, Ubuntu:18.04:LTS: linux-gcp, Ubuntu:18.04:LTS: linux-gcp-5.3, Ubuntu:18.04:LTS: linux-gke-4.15, Ubuntu:18.04:LTS: linux-gke-5.4 and 68 more

In the Linux kernel, the following vulnerability has been resolved: tmpfs: fix race on handling dquot rbtree A syzkaller reproducer found a race while attempting to remove dquot information from the rb tree. Fetching the rb_tree root node must also be protected by the dqopt->dqio_sem, otherwise, giving the right timing, shmem_release_dquot() will trigger a warning because it couldn't find a node in the tree, when the real reason was the root node changing before the search starts: Thread 1 Thread 2 - shmem_release_dquot() - shmem_{acquire,release}_dquot() - fetch ROOT - Fetch ROOT - acquire dqio_sem - wait dqio_sem - do something, triger a tree rebalance - release dqio_sem - acquire dqio_sem - start searching for the node, but from the wrong location, missing the node, and triggering a warning.

Ein lokaler Angreifer kann mehrere Schwachstellen im Linux Kernel ausnutzen, um einen Denial of Service Angriff durchzuführen oder sonstige Auswirkungen zu verursachen.