In the Linux kernel, the following vulnerability has been resolved: smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races The… (CVE-2026-98681)

The vulnerability in the Linux kernel SMB client involved the cifsFileInfo structure, where the invalidHandle, swapfile, oplock_break_cancelled, offload, and status_file_deleted fields were stored as bitfields within the same byte. These fields were updated in different code paths that could run simultaneously and were protected by different locks. Because bitfield assignments generate byte-level read-modify-write operations, concurrent modifications to different flags could overwrite each other, leading to race conditions. The fix involved converting these bitfields into separate boolean fields to avoid shared-byte read-modify-write races.

The race condition could cause inconsistent or incorrect flag states within the SMB client, potentially leading to unexpected behavior or instability in SMB file operations. No specific exploit or active attacks are known, and no direct impact such as privilege escalation or denial of service is explicitly described.

A fix has been implemented in the Linux kernel by converting the affected bitfields into separate boolean fields to prevent shared-byte read-modify-write races. Users should apply the official kernel updates that include this fix. No additional mitigation steps are indicated.