smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races

Overview

In the Linux kernel, the following vulnerability has been resolved:

smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races

The invalidHandle, swapfile, oplock_break_cancelled, offload, and status_file_deleted fields are stored in the same bitfield byte in struct cifsFileInfo, but are updated in different code paths that may run simultaneously, and are protected by different locks. Since bitfield assignments generate byte-level read-modify-write operations, a modification to one flag can overwrite a concurrent modification to another flag.

To avoid these races, convert these flags from a bitfield to separate bool fields.

Affected

• Linux >= 3bc303c254335dbd7c7012cc1760b12f1d5514d3 < 3786ee67658a2c80fef2544e7de2cd329e043cf9
• Linux >= 3bc303c254335dbd7c7012cc1760b12f1d5514d3 < 4165641d06ef44f3a31b77a28048b6c737e885e7
• Linux >= 3bc303c254335dbd7c7012cc1760b12f1d5514d3 < d9d23d115610e0342e768f6cb525d91c7b154027
• Linux >= 3bc303c254335dbd7c7012cc1760b12f1d5514d3 < 19465a9aeb664f1d710d0d22c07c31bfb7c85446
• Linux 2.6.32

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.