smb: client: require stable pages for SMB compression

Like signing, SMB compression builds the write payload from the pagecache
folios: should_compress() lets a write request through and smb_compress()
compresses those folios on the way to the socket.  If a buffered write
mutates a folio while a write subrequest is still in flight, the compressed
bytes no longer correspond to a consistent view of the data, and the server
silently stores corrupted contents - worse than the signed case, which at
least fails loudly with STATUS_ACCESS_DENIED.

Mark the mapping for stable writes when a write may be compressed, i.e. the
same condition should_compress() tests (compression negotiated and the share
allows compressed data), so netfs_perform_write() waits for writeback to
complete before modifying an in-flight folio.

Fixes: f046d71e84e1 ("smb: client: insert compression check/call on write requests")
Suggested-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

0 files changed, 0 insertions, 0 deletions