s3:smbd: try to make fsp->fh->gen_id as globally unique as possible

This makes sure the value is never 0, it's between 1 and UINT32_MAX.

While fsp->fh->gen_id is 'unsigned long' currently (which might by 8 bytes),
there's some oplock code which truncates it to uint32_t (using IVAL()).

Which means we could reuse fsp->fh->gen_id as persistent file id
until we have a final fix, which uses database.

See bug #8995 for more details.

Based on code from Ira Cooper. Ensure fsp->fh->gen_id starts from
a random point. We will use this as the SMB2 persistent_id.

metze

1 files changed, 19 insertions, 1 deletions

diff --git a/source3/smbd/files.c b/source3/smbd/files.c
index 97db348a01..fb9dacce99 100644
--- a/source3/smbd/files.c
+++ b/source3/smbd/files.c
@@ -28,12 +28,26 @@
 #define FILE_HANDLE_OFFSET 0x1000
 
 /****************************************************************************
- Return a unique number identifying this fsp over the life of this pid.
+ Return a unique number identifying this fsp over the life of this pid,
+ and try to make it as globally unique as possible.
+ See bug #8995 for the details.
 ****************************************************************************/
 
 static unsigned long get_gen_count(struct smbd_server_connection *sconn)
 {
+	/*
+	 * While fsp->fh->gen_id is 'unsigned long' currently
+	 * (which might by 8 bytes),
+	 * there's some oplock code which truncates it to
+	 * uint32_t(using IVAL()).
+	 */
+	if (sconn->file_gen_counter == 0) {
+		sconn->file_gen_counter = generate_random();
+	}
 	sconn->file_gen_counter += 1;
+	if (sconn->file_gen_counter >= UINT32_MAX) {
+		sconn->file_gen_counter = 0;
+	}
 	if (sconn->file_gen_counter == 0) {
 		sconn->file_gen_counter += 1;
 	}
@@ -315,6 +329,10 @@ files_struct *file_find_dif(struct smbd_server_connection *sconn,
 	int count=0;
 	files_struct *fsp;
 
+	if (gen_id == 0) {
+		return NULL;
+	}
+
 	for (fsp=sconn->files; fsp; fsp=fsp->next,count++) {
 		/* We can have a fsp->fh->fd == -1 here as it could be a stat open. */
 		if (file_id_equal(&fsp->file_id, &id) &&