From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
"Tobin C . Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers
Date: Tue, 03 Apr 2018 16:40:58 +0300 [thread overview]
Message-ID: <1522762858.21176.327.camel@linux.intel.com> (raw)
In-Reply-To: <20180403131346.vwjpz475fzah5a6p@pathway.suse.cz>
On Tue, 2018-04-03 at 15:13 +0200, Petr Mladek wrote:
> On Tue 2018-04-03 14:54:18, Andy Shevchenko wrote:
> > On Tue, 2018-04-03 at 13:46 +0200, Petr Mladek wrote:
> > > On Mon 2018-04-02 17:15:23, Andy Shevchenko wrote:
> > > > On Thu, 2018-03-29 at 16:53 +0200, Petr Mladek wrote:
> > > > > On Fri 2018-03-16 20:19:35, Andy Shevchenko wrote:
> > > > > > On Thu, 2018-03-15 at 16:26 +0100, Petr Mladek wrote:
> > > > > > > On Thu 2018-03-15 15:09:03, Andy Shevchenko wrote:
> > > > > > > > I still think that printing a hex value of the error
> > > > > > > > code is
> > > > > > > > much
> > > > > > > > better
> > > > > > > > than some odd "(efault)".
> > > > > > >
> > > > > > > Do you mean (err:0e)? Google gives rather confusing
> > > > > > > answers
> > > > > > > for
> > > > > > > this.
> > > > > >
> > > > > > More like "(0xHHHH)" (we have already more than 512 error
> > > > > > code
> > > > > > numbers.
> > > > >
> > > > > Hmm, I have never seen the error code in this form.
> > > >
> > > > We have limited space to print it and error numbers currently
> > > > can be
> > > > up
> > > > to 0xfff (4095). So, I have no better idea how to squeeze them
> > > > while
> > > > thinking that "(efault)" is much harder to parse in case of
> > > > error
> > > > pointer.
> > >
> > > But this will not be used instead of address value. It is used in
> > > situations
> > > where we print the information that is stored at the address, for
> > > example,
> > > string, IP address, dentry name.
> >
> > We have a lot of API functions which returns:
> > -ERR_PTR
> > NULL
> > struct foo *
> >
> > There is no guarantee that one of that API won't be used as a
> > supplier
> > for printf().
>
> OK, I think that I have finally understood it. You would like to
> detect ERR_PTR values and handle them specially? I mean to show
> the value?
>
> But then we would need to distinguish three types of errors,
> something like:
>
> + (null) for pure NULL address
> + (e:XXXX) for address in IS_ERR_VALUE() range
// Just IS_ERR(). IS_ERR_VALUE() is not meant to be used widely
> + (efault) for any other invalid address
>
> Then people might want to see values also from the first 4096 bytes.
> This is getting too complicated.
No, it's not. (null) case is already in kernel, you came with (efault),
but IS_ERR() case or any other case like it is just printing of standard
pointer value. See in the code where special_hex_number() is called.
> I am not sure if it is worth it.
Your patch will hide values for error codes. Not good for debugging.
>
>
> > You can't dereference ERR_PTR value, but anything else except the
> > actual
> > error value is worse than value itself...
>
> Yes and no, see below.
Yes, there is no "no".
>
> > >
> > > > > Also google gives
> > > > > rather confusing results when searching, for example for
> > > > > "(0x000E)".
> > > >
> > > > It's not primarily for google, though yeah, people would google
> > > > for
> > > > error messages...
> > > >
> > > > Another question is what the format: decimal versus hex for
> > > > errors.
> > > > Maybe just "(-DDDDD)"?
> > >
> > > This still looks confusing and google does not help.
> >
> > ...then we have a last option just to print a value as a pointer
> > address.
>
> We could not print the real address from security reasons. The hashed
> pointer value is not much helpful. IMHO, a common error string is
> easier to spot or search for.
Did you read what I'm writing? How on the earth the pointer in the range
of -1...-4095 would be a security issue?!
--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy
next prev parent reply other threads:[~2018-04-03 13:41 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-16 21:07 [PATCH v2 1/9] lib/test_printf: Mark big constant with ULL Andy Shevchenko
2018-02-16 21:07 ` [PATCH v2 2/9] lib/vsprintf: Make dec_spec global Andy Shevchenko
2018-04-11 9:44 ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 3/9] lib/vsprintf: Make strspec global Andy Shevchenko
2018-04-11 9:44 ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 4/9] lib/vsprintf: Make flag_spec global Andy Shevchenko
2018-04-11 9:45 ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 5/9] lib/vsprintf: Move pointer_string() upper Andy Shevchenko
2018-04-11 9:45 ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 6/9] lib/vsprintf: Deduplicate pointer_string() Andy Shevchenko
2018-04-11 9:46 ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 7/9] lib/vsprintf: Replace space with '_' before crng is ready Andy Shevchenko
2018-02-20 2:57 ` [此邮件可能存在风险] " Yang, Shunyong
2018-04-11 9:47 ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 8/9] lib/vsprintf: Remove useless NULL checks Andy Shevchenko
2018-02-27 15:50 ` Petr Mladek
2018-02-27 17:35 ` Andy Shevchenko
2018-02-28 10:04 ` Petr Mladek
2018-02-28 10:42 ` Andy Shevchenko
2018-03-02 12:51 ` Petr Mladek
2018-03-02 12:53 ` [PATCH] vsprintf: Make "null" pointer dereference more robust Petr Mladek
2018-03-02 14:17 ` Andy Shevchenko
2018-03-05 14:53 ` Petr Mladek
2018-03-29 15:13 ` Petr Mladek
2018-03-29 16:11 ` Joe Perches
2018-03-05 15:16 ` Rasmus Villemoes
2018-03-05 15:25 ` Andy Shevchenko
2018-03-06 9:25 ` Petr Mladek
2018-03-06 9:56 ` Andy Shevchenko
2018-03-07 15:52 ` Petr Mladek
2018-03-07 18:18 ` Andy Shevchenko
2018-03-07 18:34 ` Linus Torvalds
2018-03-08 14:18 ` Petr Mladek
2018-03-08 16:45 ` Linus Torvalds
2018-03-08 17:26 ` Linus Torvalds
2018-03-09 15:01 ` Petr Mladek
2018-03-09 19:05 ` Linus Torvalds
2018-03-14 14:09 ` [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers Petr Mladek
2018-03-14 22:12 ` Rasmus Villemoes
2018-03-15 15:07 ` Petr Mladek
2018-03-15 17:07 ` Steven Rostedt
2018-03-15 17:06 ` Steven Rostedt
2018-03-15 0:57 ` Sergey Senozhatsky
2018-03-15 7:58 ` Sergey Senozhatsky
2018-03-15 8:03 ` Sergey Senozhatsky
2018-03-15 17:01 ` Steven Rostedt
2018-03-16 1:18 ` Sergey Senozhatsky
2018-03-16 1:35 ` Linus Torvalds
2018-03-16 5:53 ` Sergey Senozhatsky
2018-03-16 8:55 ` Petr Mladek
2018-03-16 14:32 ` Steven Rostedt
2018-03-17 1:29 ` Sergey Senozhatsky
2018-03-15 13:07 ` Andy Shevchenko
2018-03-15 13:09 ` Andy Shevchenko
2018-03-15 15:26 ` Petr Mladek
2018-03-16 18:19 ` Andy Shevchenko
2018-03-29 14:53 ` Petr Mladek
2018-04-02 14:15 ` Andy Shevchenko
2018-04-03 1:12 ` Sergey Senozhatsky
2018-04-03 11:52 ` Petr Mladek
2018-04-03 11:56 ` Andy Shevchenko
2018-04-03 13:57 ` Sergey Senozhatsky
2018-04-03 11:46 ` Petr Mladek
2018-04-03 11:54 ` Andy Shevchenko
2018-04-03 13:13 ` Petr Mladek
2018-04-03 13:40 ` Andy Shevchenko [this message]
2018-04-03 14:50 ` Petr Mladek
2018-03-15 14:48 ` kbuild test robot
2018-03-15 20:26 ` kbuild test robot
2018-03-06 18:11 ` [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs Adam Borowski
2018-03-06 18:11 ` [PATCH 2/2] vsprintf: don't dereference pointers to the first or last page Adam Borowski
2018-03-07 13:22 ` Andy Shevchenko
2018-03-07 13:17 ` [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs Andy Shevchenko
2018-03-07 13:42 ` Adam Borowski
2018-03-07 13:29 ` Andy Shevchenko
2018-03-02 14:15 ` [PATCH v2 8/9] lib/vsprintf: Remove useless NULL checks Andy Shevchenko
2018-03-05 14:57 ` Petr Mladek
2018-02-28 10:44 ` Andy Shevchenko
2018-03-01 14:56 ` Andy Shevchenko
2018-02-16 21:07 ` [PATCH v2 9/9] lib/vsprintf: Mark expected switch fall-through Andy Shevchenko
2018-04-11 9:47 ` Petr Mladek
2018-02-18 12:58 ` [PATCH v2 1/9] lib/test_printf: Mark big constant with ULL Luc Van Oostenryck
2018-02-18 14:20 ` Andy Shevchenko
2018-02-19 15:24 ` Andy Shevchenko
2018-04-11 9:41 ` Petr Mladek
2018-02-18 21:52 ` Tobin C. Harding
2018-02-18 23:55 ` Andy Shevchenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1522762858.21176.327.camel@linux.intel.com \
--to=andriy.shevchenko@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=joe@perches.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=me@tobin.cc \
--cc=mhocko@suse.cz \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sergey.senozhatsky.work@gmail.com \
--cc=sergey.senozhatsky@gmail.com \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).