smb: client: avoid breaking the file lease when probing mfsymlinks

cifs_check_mf_symlink() probes any file whose size matches
CIFS_MF_SYMLINK_FILE_SIZE as a possible Minshall+French symlink.
smb2_query_mf_symlink() did so with a fresh leaseless SMB2_open, so the
server saw a second conflicting opener and broke the RWH lease the client
had just been granted on the same file, needlessly churning the cache.

Rework smb2_query_mf_symlink() to issue a single OPEN/READ/CLOSE compound
that either reuses an already open handle via cifs_get_readable_path() or,
failing that, opens with the inode's lease key so the server treats it as
the same lease holder.  Thread the inode down to the ->query_mf_symlink()
handlers, rename check_mf_symlink() to cifs_check_mf_symlink(), and
validate the read payload against the response buffer before copying it.

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>

0 files changed, 0 insertions, 0 deletions