CVE-2025-39884
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-23

Last updated on: 2025-12-12

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix subvolume deletion lockup caused by inodes xarray race There is a race condition between inode eviction and inode caching that can cause a live struct btrfs_inode to be missing from the root->inodes xarray. Specifically, there is a window during evict() between the inode being unhashed and deleted from the xarray. If btrfs_iget() is called for the same inode in that window, it will be recreated and inserted into the xarray, but then eviction will delete the new entry, leaving nothing in the xarray: Thread 1 Thread 2 --------------------------------------------------------------- evict() remove_inode_hash() btrfs_iget_path() btrfs_iget_locked() btrfs_read_locked_inode() btrfs_add_inode_to_root() destroy_inode() btrfs_destroy_inode() btrfs_del_inode_from_root() __xa_erase In turn, this can cause issues for subvolume deletion. Specifically, if an inode is in this lost state, and all other inodes are evicted, then btrfs_del_inode_from_root() will call btrfs_add_dead_root() prematurely. If the lost inode has a delayed_node attached to it, then when btrfs_clean_one_deleted_snapshot() calls btrfs_kill_all_delayed_nodes(), it will loop forever because the delayed_nodes xarray will never become empty (unless memory pressure forces the inode out). We saw this manifest as soft lockups in production. Fix it by only deleting the xarray entry if it matches the given inode (using __xa_cmpxchg()).
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Meta Information
Published
2025-09-23
Last Modified
2025-12-12
Generated
2026-05-07
AI Q&A
2025-09-23
EPSS Evaluated
2026-05-05
NVD
CVE-2025-39884
Affected Vendors & Products
Showing 7 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 6.11 (inc) to 6.12.48 (exc)
linux linux_kernel From 6.13 (inc) to 6.16.8 (exc)
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
linux linux_kernel 6.17
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-667 The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
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AI Powered Q&A
How can this vulnerability impact me? :

This vulnerability can cause system instability in environments using the btrfs filesystem. Specifically, it can lead to soft lockups (system hangs) during subvolume deletion due to an infinite loop caused by lost inodes with delayed nodes. This can affect system reliability and availability.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability is fixed in the Linux kernel by correcting the deletion of the xarray entry to ensure it only deletes the entry if it matches the given inode. Immediate mitigation would involve updating the Linux kernel to a version that includes this fix to prevent subvolume deletion lockups caused by the inode xarray race condition.


Can you explain this vulnerability to me?

This vulnerability is a race condition in the Linux kernel's btrfs filesystem related to inode management. Specifically, there is a timing issue between inode eviction and inode caching that can cause an inode to be lost from the internal data structure (xarray). During a small window in the eviction process, if the same inode is accessed, it can be recreated and then immediately deleted, leaving no record in the xarray. This lost inode state can cause problems during subvolume deletion, potentially leading to an infinite loop and system soft lockups.


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