Bug#23010 _my_b_read() passing illegal file handles to my_seek()

- The io cache flag seek_not_done was not set properly in the reinit_
io_chache function call and this led my_seek to be called despite an
invalid file handle.
- Added a test in reinit_io_cache to ensure we have a valid file handle
before setting seek_not_done flag.


mysys/mf_iocache.c:
  Added a test to only trigger my_seek function calls if we have 
  a valid file descriptor.
mysys/my_seek.c:
  Refactored incomplete condition into an assertion. This also ensures that
  newpos is initialized.

1 files changed, 7 insertions, 2 deletions

diff --git a/mysys/my_seek.c b/mysys/my_seek.c
index 8035312496d..006d0013695 100644
--- a/mysys/my_seek.c
+++ b/mysys/my_seek.c
@@ -29,8 +29,13 @@ my_off_t my_seek(File fd, my_off_t pos, int whence,
 		   whence, MyFlags));
   DBUG_ASSERT(pos != MY_FILEPOS_ERROR);		/* safety check */
 
-  if (-1 != fd)
-    newpos=lseek(fd, pos, whence);
+  /*
+      Make sure we are using a valid file descriptor!
+  */
+  DBUG_ASSERT(fd != -1);
+
+  newpos= lseek(fd, pos, whence);
+  
   if (newpos == (os_off_t) -1)
   {
     my_errno=errno;