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Re: Off-by-one error in windows-nat.c causes abort at startup
- From: Eli Zaretskii <eliz at gnu dot org>
- To: Pedro Alves <palves at redhat dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Mon, 02 May 2016 19:39:51 +0300
- Subject: Re: Off-by-one error in windows-nat.c causes abort at startup
- Authentication-results: sourceware.org; auth=none
- References: <83bn4rpd6m dot fsf at gnu dot org> <62c5fd08-c7b5-37e2-e364-381ae8377c03 at redhat dot com>
- Reply-to: Eli Zaretskii <eliz at gnu dot org>
> From: Pedro Alves <palves@redhat.com>
> Date: Mon, 2 May 2016 12:50:05 +0100
>
> On 04/30/2016 12:07 PM, Eli Zaretskii wrote:
>
> > Luckily, I still had GDB 7.5, which did work. Using it, I found the
> > off-by-one gotcha below (".gdbinit" is one character longer than
> > "gdb.ini"). I guess no one tested this feature when we switched from
> > using snprintf to xsnprintf...
>
> Sounds like gdb would corrupt memory before we switched to xsnprintf
> then. I'd say the problem is that the feature was added without a
> corresponding test case.
>
> > OK to commit (with a suitable ChangeLog entry, of course)?
>
> Sure.
Thanks, pushed.
> > --- gdb/windows-nat.c~ 2016-02-10 05:19:39.000000000 +0200
> > +++ gdb/windows-nat.c 2016-04-30 11:57:08.500000000 +0300
> > @@ -2711,9 +2711,9 @@ _initialize_check_for_gdb_ini (void)
> > if (access (oldini, 0) == 0)
> > {
> > int len = strlen (oldini);
> > - char *newini = (char *) alloca (len + 1);
> > + char *newini = (char *) alloca (len + 2);
> >
> > - xsnprintf (newini, len + 1, "%.*s.gdbinit",
> > + xsnprintf (newini, len + 2, "%.*s.gdbinit",
> > (int) (len - (sizeof ("gdb.ini") - 1)), oldini);
> > warning (_("obsolete '%s' found. Rename to '%s'."), oldini, newini);
>
> (I suspect this whole function could be rewritten in a clearer form...)
Like not use xsnprintf at all, and instead use strcpy/strcat, perhaps?