[Nano-devel] [PATCH 8/8] justification: limit the amount of recursion to prevent a stack overflow

[Benno Schulenberg]

---
 src/move.c  |  4 ++--
 src/proto.h |  2 +-
 src/text.c  | 15 +++++++++++----
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/move.c b/src/move.c
index e6dfd7dc..f4264350 100644
--- a/src/move.c
+++ b/src/move.c
@@ -179,7 +179,7 @@ void do_para_begin(bool update_screen)
        if (openfile->current != openfile->fileage)
                openfile->current = openfile->current->prev;
 
-       while (!begpar(openfile->current))
+       while (!begpar(openfile->current, 0))
                openfile->current = openfile->current->prev;
 
        openfile->current_x = 0;
@@ -204,7 +204,7 @@ void do_para_end(bool update_screen)
 
        while (openfile->current != openfile->filebot &&
                                inpar(openfile->current->next) &&
-                               !begpar(openfile->current->next)) {
+                               !begpar(openfile->current->next, 0)) {
                openfile->current = openfile->current->next;
        }
 
diff --git a/src/proto.h b/src/proto.h
index 2c6f1bda..68de9396 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -551,7 +551,7 @@ size_t indent_length(const char *line);
 #endif
 #ifdef ENABLE_JUSTIFY
 void justify_format(filestruct *paragraph, size_t skip);
-bool begpar(const filestruct *const foo);
+bool begpar(const filestruct *const foo, int depth);
 bool inpar(const filestruct *const foo);
 void do_justify(bool full_justify);
 void do_justify_void(void);
diff --git a/src/text.c b/src/text.c
index 2f0f7209..89723011 100644
--- a/src/text.c
+++ b/src/text.c
@@ -1035,7 +1035,7 @@ void do_enter(void)
                /* If the next line is in this same paragraph, use its 
indentation
                 * as the model, as it is more likely to be what the user 
wants. */
                if (openfile->current->next && inpar(openfile->current->next) &&
-                                                               
!begpar(openfile->current->next))
+                                                               
!begpar(openfile->current->next, 0))
                        sampleline = openfile->current->next;
 
                extra = indent_length(sampleline->data);
@@ -1983,8 +1983,11 @@ size_t quote_length(const char *line)
        return matches.rm_eo;
 }
 
+/* The maximum depth of recursion.  This must be an even number. */
+#define RECURSION_LIMIT 222
+
 /* Return TRUE when the given line is the beginning of a paragraph (BOP). */
-bool begpar(const filestruct *const line)
+bool begpar(const filestruct *const line, int depth)
 {
        size_t quote_len, indent_len, prev_dent_len;
 
@@ -1993,6 +1996,10 @@ bool begpar(const filestruct *const line)
        if (line == openfile->fileage)
                return TRUE;
 
+       /* If recursion is going too deep, just say it's not a BOP. */
+       if (depth > RECURSION_LIMIT)
+               return FALSE;
+
        quote_len = quote_length(line->data);
        indent_len = indent_length(line->data + quote_len);
 
@@ -2018,7 +2025,7 @@ bool begpar(const filestruct *const line)
                return FALSE;
 
        /* Otherwise, this is a BOP if the preceding line is not. */
-       return !begpar(line->prev);
+       return !begpar(line->prev, depth + 1);
 }
 
 /* Return TRUE when the given line is part of a paragraph. */
@@ -2149,7 +2156,7 @@ bool find_paragraph(size_t *const quote, size_t *const 
par)
 
        /* If the current line isn't the first line of the paragraph, move
         * back to the first line of the paragraph. */
-       if (!begpar(openfile->current))
+       if (!begpar(openfile->current, 0))
                do_para_begin(FALSE);
 
        /* Now current is the first line of the paragraph.  Set quote_len to
-- 
2.17.0