[Nano-devel] [PATCH 1/2] check stat's result and avoid calling stat on a NULL pointer

[Kamil Dudka]

---
 trunk/nano/src/files.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/trunk/nano/src/files.c b/trunk/nano/src/files.c
index a7aa1c5..cbd81bf 100644
--- a/trunk/nano/src/files.c
+++ b/trunk/nano/src/files.c
@@ -385,6 +385,24 @@ int do_lockfile(const char *filename)
 }
 #endif /* !NANO_TINY */
 
+#ifndef NANO_TINY
+/* If *pstat is NULL, perform a stat call with the given file name.  On 
success,
+ * *pstat points to a newly allocated buffer that contains the stat's result.
+ * On stat's failure, the NULL pointer in *pstat is left intact. */
+void stat_if_needed(const char *filename, struct stat **pstat)
+{
+    struct stat *tmp;
+    if (*pstat)
+       return;
+
+    tmp = (struct stat *)nmalloc(sizeof(struct stat));
+    if (0 == stat(filename, tmp))
+       *pstat = tmp;
+    else
+       free(tmp);
+}
+#endif
+
 /* If it's not "", filename is a file to open.  We make a new buffer, if
  * necessary, and then open and read the file, if applicable. */
 bool open_buffer(const char *filename, bool undoable)
@@ -466,11 +484,7 @@ bool open_buffer(const char *filename, bool undoable)
     if (rc > 0) {
        read_file(f, rc, filename, undoable, new_buffer);
 #ifndef NANO_TINY
-       if (openfile->current_stat == NULL) {
-           openfile->current_stat =
-               (struct stat *)nmalloc(sizeof(struct stat));
-           stat(filename, openfile->current_stat);
-       }
+       stat_if_needed(filename, &openfile->current_stat);
 #endif
     }
 
@@ -1821,10 +1835,8 @@ bool write_file(const char *name, FILE *f_open, bool 
tmp, append_type
      * specified it interactively), stat and save the value now,
      * or else we will chase null pointers when we do modtime checks,
      * preserve file times, and so on, during backup. */
-    if (openfile->current_stat == NULL && !tmp && realexists) {
-       openfile->current_stat = (struct stat *)nmalloc(sizeof(struct stat));
-       stat(realname, openfile->current_stat);
-    }
+    if (!tmp && realexists)
+       stat_if_needed(realname, &openfile->current_stat);
 
     /* We backup only if the backup toggle is set, the file isn't
      * temporary, and the file already exists.  Furthermore, if we
@@ -2214,8 +2226,10 @@ bool write_file(const char *name, FILE *f_open, bool 
tmp, append_type
        if (openfile->current_stat == NULL)
            openfile->current_stat =
                (struct stat *)nmalloc(sizeof(struct stat));
-       if (!openfile->mark_set)
-           stat(realname, openfile->current_stat);
+       if (!openfile->mark_set && 0 != stat(realname, openfile->current_stat)) 
{
+           free(openfile->current_stat);
+           openfile->current_stat = NULL;
+       }
 #endif
 
        statusbar(P_("Wrote %lu line", "Wrote %lu lines",
-- 
2.5.0