s3: smbd - Prevent file truncation on an open that fails with share mode violation.

Fix from Volker, really - just tidied up a little.
The S_ISFIFO check may not be strictly neccessary,
but doesn't hurt (might make the code a bit more complex
than it needs to be).

Fixes bug #10671 - Samba file corruption as a result of failed lock check.

https://bugzilla.samba.org/show_bug.cgi?id=10671

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: David Disseldorp <ddiss@samba.org>

diff --git a/source3/smbd/open.c b/source3/smbd/open.c
index b913c9c576debd5ca6747e553258f50253ed29ea..687caee6ab36c91da43fd08a562a8fc90f5105e3 100644 (file)
--- a/source3/smbd/open.c
+++ b/source3/smbd/open.c
@@ -840,8 +840,11 @@ static NTSTATUS open_file(files_struct *fsp,
                        }
                }
 
-               /* Actually do the open */
-               status = fd_open_atomic(conn, fsp, local_flags,
+               /*
+                * Actually do the open - if O_TRUNC is needed handle it
+                * below under the share mode lock.
+                */
+               status = fd_open_atomic(conn, fsp, local_flags & ~O_TRUNC,
                                unx_mode, p_file_created);
                if (!NT_STATUS_IS_OK(status)) {
                        DEBUG(3,("Error opening file %s (%s) (local_flags=%d) "
@@ -2676,6 +2679,21 @@ static NTSTATUS open_file_ntcreate(connection_struct *conn,
                return status;
        }
 
+       /* Should we atomically (to the client at least) truncate ? */
+       if (!new_file_created) {
+               if (flags2 & O_TRUNC) {
+                       if (!S_ISFIFO(fsp->fsp_name->st.st_ex_mode)) {
+                               int ret = vfs_set_filelen(fsp, 0);
+                               if (ret != 0) {
+                                       status = map_nt_error_from_unix(errno);
+                                       TALLOC_FREE(lck);
+                                       fd_close(fsp);
+                                       return status;
+                               }
+                       }
+               }
+       }
+
        grant_fsp_oplock_type(fsp, lck, oplock_request);
 
        /*