[PATCH 26/29] ksmbd: treat read-control opens as stat opens only for leases

[Namjae Jeon <linkinjeon@kernel.org>]

A second open that requests only metadata-level access must not break
the existing caching state. ksmbd already skips the break for such opens
via fp->attrib_only (FILE_READ_ATTRIBUTES,
FILE_WRITE_ATTRIBUTES and FILE_SYNCHRONIZE).

An open requesting only READ_CONTROL (reading the security descriptor)
must be treated differently depending on the existing caching state.
smbtorture smb2.lease.statopen4 expects a read-control open NOT to break
a caching lease, while smb2.oplock.statopen1 expects the same open to
break a batch oplock. So READ_CONTROL is a stat open for leases but not
for oplocks.

Extend the stat-open break-skip in smb_grant_oplock() to also cover a
read-control-only open, but only when the existing holder is a lease.
The global fp->attrib_only flag (used for share-mode, rename and truncate
decisions) is left unchanged so oplock behaviour is preserved.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 fs/smb/server/oplock.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/fs/smb/server/oplock.c b/fs/smb/server/oplock.c
index fa7efd45b8e5..5b5783d75389 100644
--- a/fs/smb/server/oplock.c
+++ b/fs/smb/server/oplock.c
@@ -312,6 +312,18 @@ void opinfo_put(struct oplock_info *opinfo)
 	free_opinfo(opinfo);
 }
 
+static bool ksmbd_inode_has_lease(struct ksmbd_inode *ci)
+{
+	struct oplock_info *opinfo = opinfo_get_list(ci);
+	bool is_lease;
+
+	if (!opinfo)
+		return false;
+	is_lease = opinfo->is_lease;
+	opinfo_put(opinfo);
+	return is_lease;
+}
+
 static void opinfo_add(struct oplock_info *opinfo, struct ksmbd_file *fp)
 {
 	struct ksmbd_inode *ci = fp->f_ci;
@@ -1402,10 +1414,22 @@ int smb_grant_oplock(struct ksmbd_work *work, int req_op_level, u64 pid,
 	if (!opinfo_count(fp))
 		goto set_lev;
 
-	/* grant none-oplock if second open is trunc */
-	if (fp->attrib_only && fp->cdoption != FILE_OVERWRITE_IF_LE &&
+	/*
+	 * A stat open that only requests metadata access must not break the
+	 * existing caching state. READ_CONTROL (reading the security
+	 * descriptor) does not conflict with a lease, but it does conflict
+	 * with an oplock, so only treat a read-control-only open as a stat
+	 * open when the existing holder is a lease.
+	 */
+	if (fp->cdoption != FILE_OVERWRITE_IF_LE &&
 	    fp->cdoption != FILE_OVERWRITE_LE &&
-	    fp->cdoption != FILE_SUPERSEDE_LE) {
+	    fp->cdoption != FILE_SUPERSEDE_LE &&
+	    (fp->attrib_only ||
+	     (!(fp->daccess & ~(FILE_READ_ATTRIBUTES_LE |
+				FILE_WRITE_ATTRIBUTES_LE |
+				FILE_SYNCHRONIZE_LE |
+				FILE_READ_CONTROL_LE)) &&
+	      ksmbd_inode_has_lease(ci)))) {
 		req_op_level = SMB2_OPLOCK_LEVEL_NONE;
 		goto set_lev;
 	}
-- 
2.25.1