CVE-2025-71159
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk11th percentile - higher than 11% of all known CVEs
Summary
In the Linux kernel btrfs filesystem, btrfs_get_or_create_delayed_node() had a memory ordering bug after moving refcount_set inside the critical section, potentially leading to a use-after-free.
Risk Assessment
This vulnerability could allow a local attacker to trigger a system crash or potentially escalate privileges by exploiting the reference counting bug.
Recommendation
Install the Linux kernel patch that moves refcount_set back before the critical section to ensure proper memory barrier.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node() Previously, btrfs_get_or_create_delayed_node() set the delayed_node's refcount before acquiring the root->delayed_nodes lock. Commit e8513c012de7 ("btrfs: implement ref_tracker for delayed_nodes") moved refcount_set inside the critical section, which means there is no longer a memory barrier between setting the refcount and setting btrfs_inode->delayed_node. Without that barrier, the stores to node->refs and btrfs_inode->delayed_node may become visible out of order. Another thread can then read btrfs_inode->delayed_node and attempt to increment a refcount that hasn't been set yet, leading to a refcounting bug and a use-after-free warning. The fix is to move refcount_set back to where it was to take advantage of the implicit memory barrier provided by lock acquisition. Because the allocations now happen outside of the lock's critical section, they can use GFP_NOFS instead of GFP_ATOMIC.