1 files changed, 16 insertions, 5 deletions

diff --git a/src/fileio.c b/src/fileio.c
index b82b7d360b5..3155ef0edf1 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -3470,7 +3470,11 @@ by calling `format-decode', which see.  */)
       mtime = time_error_value (save_errno);
       st.st_size = -1;
       if (!NILP (Vcoding_system_for_read))
-        Fset (Qbuffer_file_coding_system, Vcoding_system_for_read);
+        {
+          /* Don't let invalid values into buffer-file-coding-system.  */
+          CHECK_CODING_SYSTEM (Vcoding_system_for_read);
+          Fset (Qbuffer_file_coding_system, Vcoding_system_for_read);
+        }
       goto notfound;
     }
 
@@ -4569,7 +4573,7 @@ choose_write_coding_system (Lisp_Object start, Lisp_Object end, Lisp_Object file
       if (NILP (val))
         {
           /* If we still have not decided a coding system, use the
-             default value of buffer-file-coding-system.  */
+             current buffer's value of buffer-file-coding-system.  */
           val = BVAR (current_buffer, buffer_file_coding_system);
           using_default_coding = 1;
         }
@@ -4587,9 +4591,16 @@ choose_write_coding_system (Lisp_Object start, Lisp_Object end, Lisp_Object file
 
       if (!force_raw_text
           && !NILP (Ffboundp (Vselect_safe_coding_system_function)))
-        /* Confirm that VAL can surely encode the current region.  */
-        val = call5 (Vselect_safe_coding_system_function,
-                     start, end, val, Qnil, filename);
+        {
+          /* Confirm that VAL can surely encode the current region.  */
+          val = call5 (Vselect_safe_coding_system_function,
+                       start, end, val, Qnil, filename);
+          /* As the function specified by select-safe-coding-system-function
+             is out of our control, make sure we are not fed by bogus
+             values.  */
+          if (!NILP (val))
+            CHECK_CODING_SYSTEM (val);
+        }
 
       /* If the decided coding-system doesn't specify end-of-line
          format, we use that of