MDEV-23867: insert... select crash in compute_window_func10.2-mdev23867

There are 2 issues here:

Issue #1: memory allocation.
An IO_CACHE that uses encryption uses a larger buffer (it needs space for the encrypted data,
decrypted data, IO_CACHE_CRYPT struct to describe encryption parameters etc).

Issue #2: IO_CACHE::seek_not_done
When IO_CACHE objects are cloned, they still share the file descriptor.
This means, operation on one IO_CACHE may change the file read position
which will confuse other IO_CACHEs using it.

The fix of these issues would be:
Allocate the buffer to also include the extra size needed for encryption.
Perform seek again after one IO_CACHE reads a file.

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/mf_iocache_encr.cc b/sql/mf_iocache_encr.cc
index d741cf8b837..29d7074aeb1 100644
--- a/sql/mf_iocache_encr.cc
+++ b/sql/mf_iocache_encr.cc
@@ -71,6 +71,16 @@ static int my_b_encr_read(IO_CACHE *info, uchar *Buffer, size_t Count)
       DBUG_RETURN(1);
     }
     info->seek_not_done= 0;
+    if (info->next_file_user)
+    {
+      IO_CACHE *c;
+      for (c= info->next_file_user;
+           c!= info;
+           c= c->next_file_user)
+      {
+        c->seek_not_done= 1;
+      }
+    }
   }
 
   do