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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Trond Myklebust <trond.myklebust@primarydata.com>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	"David S. Miller" <davem@davemloft.net>,
	linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
	netdev@vger.kernel.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@rasmusvillemoes.dk>

On Tue, 2015-03-03 at 00:03 +0100, Rasmus Villemoes wrote:
> On Mon, Mar 02 2015, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> > On Mon, 2015-02-23 at 23:55 +0100, Rasmus Villemoes wrote:
> >> On Mon, Feb 23 2015, Andy Shevchenko <andriy.shevchenko@linux.intel.com> 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@intel.com>
Intel Finland Oy


WARNING: multiple messages have this Message-ID
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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  reply	other threads:[~2015-03-03 10:26 UTC|newest]

Thread overview: 52+ 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 1/2] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-01-28 14:53   ` Andy Shevchenko
2015-01-28 15:49     ` Rasmus Villemoes
2015-01-28 16:43       ` Andy Shevchenko
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 1/3] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-01-29 10:43     ` Andy Shevchenko
2015-01-29 10:03   ` [PATCH v2 2/3] lib/string_helpers.c: Refactor string_escape_mem Rasmus Villemoes
2015-01-29 12:12     ` Andy Shevchenko
2015-01-29 13:10       ` Rasmus Villemoes
2015-01-29 13:37         ` Andy Shevchenko
2015-01-29 19:33           ` Jeff Epler
2015-01-30 10:14             ` Andy Shevchenko
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
2015-01-30 23:39           ` Rasmus Villemoes
2015-01-30 23:39             ` Rasmus Villemoes
2015-02-02 10:56             ` Andy Shevchenko
2015-02-09 23:44   ` [PATCH v3 0/3] Two printf fixes Rasmus Villemoes
2015-02-09 23:44     ` Rasmus Villemoes
2015-02-09 23:44     ` [PATCH v3 1/3] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-02-09 23:44     ` [PATCH v3 2/3] lib/string_helpers.c: Refactor string_escape_mem Rasmus Villemoes
2015-02-10 12:16       ` Andy Shevchenko
2015-02-09 23:44     ` [PATCH v3 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-02-09 23:44       ` Rasmus Villemoes
2015-02-10 12:32       ` Andy Shevchenko
2015-02-10 12:32         ` Andy Shevchenko
2015-02-10 13:02         ` Rasmus Villemoes
2015-02-10 14:22           ` Andy Shevchenko
2015-02-10 14:22             ` Andy Shevchenko
2015-02-21  1:35             ` Rasmus Villemoes
2015-02-23 12:50               ` Andy Shevchenko
2015-02-23 12:50                 ` Andy Shevchenko
2015-02-23 22:55                 ` Rasmus Villemoes
2015-02-23 22:55                   ` Rasmus Villemoes
2015-03-02 12:37                   ` Andy Shevchenko
2015-03-02 12:37                     ` Andy Shevchenko
2015-03-02 23:03                     ` Rasmus Villemoes
2015-03-03 10:26                       ` Andy Shevchenko [this message]
2015-03-03 10:26                         ` Andy Shevchenko
2015-03-03 23:20     ` [PATCH v4 0/3] Two printf fixes Rasmus Villemoes
2015-03-03 23:20       ` [PATCH v4 1/3] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-03-03 23:20       ` [PATCH v4 2/3] lib/string_helpers.c: Refactor string_escape_mem Rasmus Villemoes
2015-03-04 10:51         ` Andy Shevchenko
2015-03-03 23:20       ` [PATCH v4 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-03-04 11:49         ` Andy Shevchenko
2015-03-04 11:49           ` Andy Shevchenko

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