From: Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
To: Rasmus Villemoes
<linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
Cc: Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Trond Myklebust
<trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org>,
"J. Bruce Fields"
<bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>,
"David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH v3 3/3] lib/string_helpers.c: Change semantics of string_escape_mem
Date: Tue, 03 Mar 2015 12:26:45 +0200 [thread overview]
Message-ID: <1425378405.14897.139.camel@linux.intel.com> (raw)
In-Reply-To: <87a8zvovcj.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
On Tue, 2015-03-03 at 00:03 +0100, Rasmus Villemoes wrote:
> On Mon, Mar 02 2015, Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> wrote:
> > On Mon, 2015-02-23 at 23:55 +0100, Rasmus Villemoes wrote:
> >> On Mon, Feb 23 2015, Andy Shevchenko <andriy.shevchenko-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> wrote:
> >
> >> > What about to make it a separate function *and* call from inside of
> >> > test_string_escape? Would it work for you?
> >>
> >> See my earlier point about "quite a lot of state to pass". But if this
> >>
> >> static __init void
> >> test_string_escape_overflow(const char *in, int p, char *out_real, int out_size,
> >> unsigned int flags, const char *esc, int q_test,
> >> const char *name)
> >> {
> >> int q_real;
> >>
> >> memset(out_real, 'Z', out_size);
> >> q_real = string_escape_mem(in, p, out_real, 0, flags, esc);
> >> if (q_real != q_test)
> >> pr_warn("Test '%s' failed: flags = %u, osz = 0, expected %d, got %d\n",
> >> name, flags, q_test, q_real);
> >> if (memchr_inv(out_real, 'Z', out_size))
> >> pr_warn("Test '%s' failed: osz = 0 but string_escape_mem wrote to the buffer\n",
> >> name);
> >> }
> >>
> >> is what you want, sure, have it your way.
> >
> > Something like above, though might be few variables can be defined
> > inside it, such as out_real, out_size.
>
> Or maybe not at all: We could pass NULL, 0, which is what has to work
> anyway for the kasprintf case - failure will then be detected through an
> oops, but I think that should be ok. That would also remove the memset and
> memchr_inv calls above.
>
> I don't like the idea of just defining a small stack buffer (say
> buf[16]) and passing that (still with a size of 0): It's better to
> either detect writes directly (by passing a large enough buffer with
> known contents), or indirectly through an oops, as opposed to having to
> figure it out from random stack corruption. And kmalloc'ing+error
> handling+kfree'ing a buffer inside the overflow check would just be
> plain silly, when we have a large enough buffer already.
Come with v4, I think I have no big objections to the approach.
> As I said, I do think that longer-term one shouldn't have to poke around
> in the seq_file internals, but for now I'd like to make the patch minimal.
Ok.
> >> Another option is to do everything with a single seq_printf call,
> >> something like
> >>
> >> seq_printf(m, "Name:\t%*pEcs\n, (int)strlen(tcomm), tcomm)
> >>
> >> That will escape more than just \ and \n, but that would IMO be an
> >> improvement. But of course this is out of scope for this series.]
> >
> > It should be %pT and reconsider policy how we print task name in
> > different cases (vsprintf.c::comm_name()).
>
> Well, %pT is a completely new addition to vsprintf.c. Also, I don't
> think that would be a very good match - not every user of %pT might want
> escaping, so at the very least this would require implementing some
> extra flags for %pT.
Something like %pTe (for 'sanely Escaped' with flags you proposed
earlier) ?
> But if task_name would be the only user of those
> flags, I think the escaping logic is better kept there. Anyway, this is
> outside this series' scope.
Yes.
--
Andy Shevchenko <andriy.shevchenko-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Intel Finland Oy
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next prev parent reply other threads:[~2015-03-03 10:26 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-28 13:25 [PATCH 0/2] Two printf fixes Rasmus Villemoes
2015-01-28 13:25 ` [PATCH 2/2] string_helpers: Change semantics of string_escape_mem Rasmus Villemoes
2015-01-28 15:05 ` Andy Shevchenko
2015-01-29 10:03 ` [PATCH v2 0/3] Two printf fixes Rasmus Villemoes
2015-01-29 10:03 ` [PATCH v2 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-01-29 13:29 ` Andy Shevchenko
2015-01-29 14:29 ` Rasmus Villemoes
2015-01-30 10:27 ` Andy Shevchenko
[not found] ` <1422613655.31903.351.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2015-01-30 23:39 ` Rasmus Villemoes
2015-02-02 10:56 ` Andy Shevchenko
[not found] ` <1422525801-26560-1-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-09 23:44 ` [PATCH v3 0/3] Two printf fixes Rasmus Villemoes
[not found] ` <1423525491-12613-1-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-09 23:44 ` [PATCH v3 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
[not found] ` <1423525491-12613-4-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-10 12:32 ` Andy Shevchenko
2015-02-10 13:02 ` Rasmus Villemoes
[not found] ` <87386dj4x0.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-10 14:22 ` Andy Shevchenko
2015-02-21 1:35 ` Rasmus Villemoes
[not found] ` <87oaoo59n2.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-02-23 12:50 ` Andy Shevchenko
[not found] ` <1424695820.14897.10.camel-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2015-02-23 22:55 ` Rasmus Villemoes
[not found] ` <87k2z86xvs.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-03-02 12:37 ` Andy Shevchenko
2015-03-02 23:03 ` Rasmus Villemoes
[not found] ` <87a8zvovcj.fsf-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-03-03 10:26 ` Andy Shevchenko [this message]
2015-03-03 23:20 ` [PATCH v4 0/3] Two printf fixes Rasmus Villemoes
2015-03-03 23:20 ` [PATCH v4 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
[not found] ` <1425424836-17947-4-git-send-email-linux-qQsb+v5E8BnlAoU/VqSP6n9LOBIZ5rWg@public.gmane.org>
2015-03-04 11:49 ` Andy Shevchenko
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