Re: [PATCH unionfs 3/3] Don't use strncat() with length derived from source string

[Samuel Thibault]

Jessica Clarke, le lun. 26 avril 2021 19:02:54 +0100, a ecrit:
> On 26 Apr 2021, at 18:08, Sergey Bugaev <bugaevc@gmail.com> wrote:
> > This fixes Wstringop-overflow and Wstringop-truncation GCC warnings.
> > See https://gcc.gnu.org/bugzilla//show_bug.cgi?id=88059
> > 
> > Also, fix a bug where a string was not properly null-terminated.
> > ---
> > lib.c  | 4 ++--
> > stow.c | 5 +++--
> > 2 files changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/lib.c b/lib.c
> > index 01cdbd0..717979b 100644
> > --- a/lib.c
> > +++ b/lib.c
> > @@ -151,8 +151,8 @@ make_filepath (char *path, char *filename)
> >   if (filepath == NULL) 
> >     return NULL;
> > 
> > -  strncpy (filepath, path, length);
> > -  strncat (filepath, filename, strlen (filename));
> > +  strcpy (filepath, path);
> > +  strcat (filepath, filename);
> 
> This is dubious. We should be using safe interfaces where possible.

Yes, we don't want to just ignore the warnings, and actually check where
the length is wrong.

Samuel