Executive brief
A vulnerability was identified in the Linux kernel's network filesystem library (netfslib) that could lead to data corruption. On certain systems, file size information could be updated incorrectly when multiple processes access the same file simultaneously. This could result in inconsistent file data or system instability when using network-attached storage like AFS or SMB.
Technical details
A race condition exists in the Linux kernel's netfslib due to improper synchronization when updating 'remote_i_size' and 'zero_point' attributes. On 32-bit architectures, 64-bit variables can suffer from 'tearing' where a read operation captures a partially updated value if proper locking is not enforced. The fix involves ensuring the 'i_lock' spinlock is held during updates and utilizing 'seqcount' to maintain coherency, mirroring the standard 'i_size_read' and 'i_size_write' mechanisms. This affects filesystems utilizing netfslib, including 9p, AFS, and SMB (CIFS).
Affected products
- Linux Linux 5.18 to 7.0.11
Timeline
- 2026-07-19: disclosed
- 2026-07-19: advisory