[PATCH 5.9 017/152] smb3: Avoid Mid pending list corruption

[Greg Kroah-Hartman]

From: Rohith Surabattula <rohiths@xxxxxxxxxxxxx>

commit ac873aa3dc21707c47db5db6608b38981c731afe upstream.

When reconnect happens Mid queue can be corrupted when both
demultiplex and offload thread try to dequeue the MID from the
pending list.

These patches address a problem found during decryption offload:
         CIFS: VFS: trying to dequeue a deleted mid
that could cause a refcount use after free:
         Workqueue: smb3decryptd smb2_decrypt_offload [cifs]

Signed-off-by: Rohith Surabattula <rohiths@xxxxxxxxxxxxx>
Reviewed-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx>
CC: Stable <stable@xxxxxxxxxxxxxxx> #5.4+
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/cifs/smb2ops.c |   55 +++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 46 insertions(+), 9 deletions(-)

--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -262,7 +262,7 @@ smb2_revert_current_mid(struct TCP_Serve
 }
 
 static struct mid_q_entry *
-smb2_find_mid(struct TCP_Server_Info *server, char *buf)
+__smb2_find_mid(struct TCP_Server_Info *server, char *buf, bool dequeue)
 {
 	struct mid_q_entry *mid;
 	struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buf;
@@ -279,6 +279,10 @@ smb2_find_mid(struct TCP_Server_Info *se
 		    (mid->mid_state == MID_REQUEST_SUBMITTED) &&
 		    (mid->command == shdr->Command)) {
 			kref_get(&mid->refcount);
+			if (dequeue) {
+				list_del_init(&mid->qhead);
+				mid->mid_flags |= MID_DELETED;
+			}
 			spin_unlock(&GlobalMid_Lock);
 			return mid;
 		}
@@ -287,6 +291,18 @@ smb2_find_mid(struct TCP_Server_Info *se
 	return NULL;
 }
 
+static struct mid_q_entry *
+smb2_find_mid(struct TCP_Server_Info *server, char *buf)
+{
+	return __smb2_find_mid(server, buf, false);
+}
+
+static struct mid_q_entry *
+smb2_find_dequeue_mid(struct TCP_Server_Info *server, char *buf)
+{
+	return __smb2_find_mid(server, buf, true);
+}
+
 static void
 smb2_dump_detail(void *buf, struct TCP_Server_Info *server)
 {
@@ -4260,7 +4276,10 @@ handle_read_data(struct TCP_Server_Info
 		cifs_dbg(FYI, "%s: server returned error %d\n",
 			 __func__, rdata->result);
 		/* normal error on read response */
-		dequeue_mid(mid, false);
+		if (is_offloaded)
+			mid->mid_state = MID_RESPONSE_RECEIVED;
+		else
+			dequeue_mid(mid, false);
 		return 0;
 	}
 
@@ -4284,7 +4303,10 @@ handle_read_data(struct TCP_Server_Info
 		cifs_dbg(FYI, "%s: data offset (%u) beyond end of smallbuf\n",
 			 __func__, data_offset);
 		rdata->result = -EIO;
-		dequeue_mid(mid, rdata->result);
+		if (is_offloaded)
+			mid->mid_state = MID_RESPONSE_MALFORMED;
+		else
+			dequeue_mid(mid, rdata->result);
 		return 0;
 	}
 
@@ -4300,21 +4322,30 @@ handle_read_data(struct TCP_Server_Info
 			cifs_dbg(FYI, "%s: data offset (%u) beyond 1st page of response\n",
 				 __func__, data_offset);
 			rdata->result = -EIO;
-			dequeue_mid(mid, rdata->result);
+			if (is_offloaded)
+				mid->mid_state = MID_RESPONSE_MALFORMED;
+			else
+				dequeue_mid(mid, rdata->result);
 			return 0;
 		}
 
 		if (data_len > page_data_size - pad_len) {
 			/* data_len is corrupt -- discard frame */
 			rdata->result = -EIO;
-			dequeue_mid(mid, rdata->result);
+			if (is_offloaded)
+				mid->mid_state = MID_RESPONSE_MALFORMED;
+			else
+				dequeue_mid(mid, rdata->result);
 			return 0;
 		}
 
 		rdata->result = init_read_bvec(pages, npages, page_data_size,
 					       cur_off, &bvec);
 		if (rdata->result != 0) {
-			dequeue_mid(mid, rdata->result);
+			if (is_offloaded)
+				mid->mid_state = MID_RESPONSE_MALFORMED;
+			else
+				dequeue_mid(mid, rdata->result);
 			return 0;
 		}
 
@@ -4329,7 +4360,10 @@ handle_read_data(struct TCP_Server_Info
 		/* read response payload cannot be in both buf and pages */
 		WARN_ONCE(1, "buf can not contain only a part of read data");
 		rdata->result = -EIO;
-		dequeue_mid(mid, rdata->result);
+		if (is_offloaded)
+			mid->mid_state = MID_RESPONSE_MALFORMED;
+		else
+			dequeue_mid(mid, rdata->result);
 		return 0;
 	}
 
@@ -4340,7 +4374,10 @@ handle_read_data(struct TCP_Server_Info
 	if (length < 0)
 		return length;
 
-	dequeue_mid(mid, false);
+	if (is_offloaded)
+		mid->mid_state = MID_RESPONSE_RECEIVED;
+	else
+		dequeue_mid(mid, false);
 	return length;
 }
 
@@ -4369,7 +4406,7 @@ static void smb2_decrypt_offload(struct
 	}
 
 	dw->server->lstrp = jiffies;
-	mid = smb2_find_mid(dw->server, dw->buf);
+	mid = smb2_find_dequeue_mid(dw->server, dw->buf);
 	if (mid == NULL)
 		cifs_dbg(FYI, "mid not found\n");
 	else {