smb: client: flush dirty data before zeroing a range

Overview

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

smb: client: flush dirty data before zeroing a range

smb3_zero_range() emulates FALLOC_FL_ZERO_RANGE by invalidating the page cache over the target range with truncate_pagecache_range() and then issuing FSCTL_SET_ZERO_DATA to the server.

Dirty data was only flushed conditionally, when the range reached or extended EOF. For a purely interior zero range that does not reach EOF, no flush happened, so a dirty folio overlapping the range could be written back to the server after the FSCTL and refill the range that was just zeroed with stale data.

Fix this by unconditionally flushing and waiting for dirty data in the range before invalidating the page cache and issuing FSCTL_SET_ZERO_DATA, exactly as was done for smb3_punch_hole() in commit d7d2adcd022b ("smb/client: flush dirty data before punching a hole"); the two paths are structurally identical here.

This is observed as generic/363 randomly reading stale data where a zeroed range is expected against Windows Server.

Affected

• Linux >= 91d1dfae464987aaf6c79ff51d8674880fb3be77 < cecf4114069fc19629d284710fd783d56bbca862
• Linux >= 91d1dfae464987aaf6c79ff51d8674880fb3be77 < e8ba21c7e6ef3d4cb617858760673877b2e4a2bb
• Linux >= 91d1dfae464987aaf6c79ff51d8674880fb3be77 < 8f8d32c1044f70e46e87550e039a15ff20a4b21c
• Linux 13af7446428771e9e529284d390e7994df8be683
• Linux 0a9423f99ded38b32bd1864347332cc557e6b141
• Linux 7dfa4279c55f467a88e653a5d544817181b22aea
• Linux >= 6.1.110 < 6.2
• Linux >= 6.6.51 < 6.7
• Linux >= 6.10.10 < 6.11
• Linux 6.11

Remediation

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