Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: return error when node already exists in hfs_bnode_create
When hfs_bnode_create() finds that a node is already hashed (which should not happen in normal operation), it currently returns the existing node without incrementing its reference count. This causes a reference count inconsistency that leads to a kernel panic when the node is later freed in hfs_bnode_put():
kernel BUG at fs/hfsplus/bnode.c:676! BUG_ON(!atomic_read(&node->refcnt))
This scenario can occur when hfs_bmap_alloc() attempts to allocate a node that is already in use (e.g., when node 0’s bitmap bit is incorrectly unset), or due to filesystem corruption.
Returning an existing node from a create path is not normal operation.
Fix this by returning ERR_PTR(-EEXIST) instead of the node when it’s already hashed. This properly signals the error condition to callers, which already check for IS_ERR() return values.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS
- Affected packages:
- linux @ 5.4.0 (+15 more)
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: return error when node already exists in hfs_bnode_create
When hfs_bnode_create() finds that a node is already hashed (which should not happen in normal operation), it currently returns the existing node without incrementing its reference count. This causes a reference count inconsistency that leads to a kernel panic when the node is later freed in hfs_bnode_put():
kernel BUG at fs/hfsplus/bnode.c:676! BUG_ON(!atomic_read(&node->refcnt))
This scenario can occur when hfs_bmap_alloc() attempts to allocate a node that is already in use (e.g., when node 0’s bitmap bit is incorrectly unset), or due to filesystem corruption.
Returning an existing node from a create path is not normal operation.
Fix this by returning ERR_PTR(-EEXIST) instead of the node when it’s already hashed. This properly signals the error condition to callers, which already check for IS_ERR() return values.