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

[Benno Schulenberg]

On Wed, Feb 3, 2016, at 12:32, Kamil Dudka wrote:
> 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
> @@ -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;
> +     }

I don't get this part.  Why (also in the original code) malloc the
stat struct when not actually going to stat()?  Or asked another
way: why free the stat struct only when the mark is not set?

So I think this part should be:

-       /* Update current_stat to reference the file as it is now. */
-       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) {
+           if (openfile->current_stat == NULL)
+               openfile->current_stat =
+                       (struct stat *)nmalloc(sizeof(struct stat));
+
+           /* Update the stat info to reflect the file as it is now. */
+           if (stat(realname, openfile->current_stat) != 0) {
+               free(openfile->current_stat);
+               openfile->current_stat = NULL;
+           }
+       }

But still... as the comment says, it assumes that there is
already stat info there, so the malloc should be superfluous
in this case.  But the whole routine is so convoluted that I
don't dare remove it.

Benno

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ensure-stat-info-is-valid.patch
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