smb: client: discard post-EOF pagecache when extending a file via clone range

Overview

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

smb: client: discard post-EOF pagecache when extending a file via clone range

cifs_remap_file_range() discarded the pagecache only for the folios overlapping the destination region, so when a clone extends the file the folio straddling the old EOF - which may hold data dirtied past EOF through an mmap - was never dropped and became visible as file content once the file was extended.

Start the discard at the smaller of fstart and the old EOF. i_size is still old here, so nothing past the old EOF is flushed to the server.

Affected

• Linux >= c54fc3a4f375663f2361a9cbb2955fb4ef912879 < 15bb9f1d3e967e328649e92a1451e60a0dc66118
• Linux >= c54fc3a4f375663f2361a9cbb2955fb4ef912879 < 4721587f96cb8de8164f3fd203093a0875560999
• Linux 358bd5f436d820bb758833050aae065b35d6986c
• Linux 43801359c8971cc49b4a4db5015fba77fbd09c32
• Linux >= 6.1.68 < 6.2
• Linux >= 6.6.7 < 6.7
• Linux 6.7

Remediation

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