[groff] 08/08: [troff]: Fix unsafe-mode null pointer dereference.

[G. Branden Robinson]

gbranden pushed a commit to branch master
in repository groff.

commit e8ffda953c84c34c73101369f69cdc6630d788ff
Author: G. Branden Robinson <g.branden.robinson@gmail.com>
AuthorDate: Tue Sep 17 07:59:23 2024 -0500

    [troff]: Fix unsafe-mode null pointer dereference.
    
    * src/roff/troff/input.cpp (open_file): Fix unsafe-mode SEGV caused by
      null pointer dereference.  Problem introduced by me in commit
      6d32f2492e, 13 September.  Also add assertion; null `FILE` stream
      pointers should not be getting stored in GNU troff's
      `stream_dictionary`.
---
 ChangeLog                |  8 ++++++++
 src/roff/troff/input.cpp | 14 +++++++++-----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index d860c7860..ce16fb55f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2024-09-17  G. Branden Robinson <g.branden.robinson@gmail.com>
+
+       * src/roff/troff/input.cpp (open_file): Fix unsafe-mode SEGV
+       caused by null pointer dereference.  Problem introduced by me in
+       commit 6d32f2492e, 13 September.  Also add assertion; null
+       `FILE` stream pointers should not be getting stored in GNU
+       troff's `stream_dictionary`.
+
 2024-09-17  G. Branden Robinson <g.branden.robinson@gmail.com>
 
        * src/roff/troff/input.cpp (report_color): Report color space
diff --git a/src/roff/troff/input.cpp b/src/roff/troff/input.cpp
index 3a2f713f4..6de8078c6 100644
--- a/src/roff/troff/input.cpp
+++ b/src/roff/troff/input.cpp
@@ -7282,11 +7282,15 @@ static void open_file(bool appending)
       else {
        grostream *oldgrost
          = (grostream *)stream_dictionary.lookup(stream);
-       FILE *oldfp = oldgrost->file;
-       if (oldfp != 0 /* nullptr */ && (fclose(oldfp) != 0)) {
-         error("cannot close file '%1' already associated with stream"
-               " '%2': %3", filename.contents(), strerror(errno));
-         return;
+       if (oldgrost != 0 /* nullptr */) {
+         FILE *oldfp = oldgrost->file;
+         assert(oldfp != 0 /* nullptr */);
+         if (oldfp != 0 /* nullptr */ && (fclose(oldfp) != 0)) {
+           error("cannot close file '%1' already associated with"
+                 " stream '%2': %3", filename.contents(),
+                 strerror(errno));
+           return;
+         }
        }
        grostream *grost = new grostream(filename.contents(), mode,
                                         &*fp);