From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Adam Borowski <kilobyte@angband.pl>,
Petr Mladek <pmladek@suse.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
"Tobin C . Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs
Date: Wed, 07 Mar 2018 15:17:19 +0200 [thread overview]
Message-ID: <1520428639.10722.461.camel@linux.intel.com> (raw)
In-Reply-To: <20180306181122.11449-1-kilobyte@angband.pl>
On Tue, 2018-03-06 at 19:11 +0100, Adam Borowski wrote:
Thanks for the patch, my comments below.
> Attempting to print an object pointed to by a bad (usually ERR_PTR)
> pointer
> is a not so surprising error. Our code handles them inconsistently:
> * two places print (null) if ptr<PAGE_SIZE
> * one place prints (null) if abs(ptr)<PAGE_SIZE
> * one place prints (null) only if !ptr
>
> Obviously, saying (null) for a small but non-0 value is misleading.
> Thus, let's print:
> * (null) for exactly 0
> * (err) if last page && abs(ptr)<=MAX_ERRNO
> * (invalid) otherwise
>
First of all, this patch is much more arguable than the other one in
your small series.
"(invalid)" is invalid. Hint: there is a nice comment in the code why.
I'm in principle not putting explanation here to insist people to
eventually _read and understand_ the code before doing anything.
Some comments below.
> +#define BAD_PTR_STRING(x) (!(x) ? "(null)" : IS_ERR(x) ? "(err)" :
> "(invalid)")
It looks ugly.
> /**
> * simple_strtoull - convert a string to an unsigned long long
> * @cp: The start of the string
> @@ -588,7 +590,7 @@ char *string(char *buf, char *end, const char *s,
> struct printf_spec spec)
> size_t lim = spec.precision;
>
> if ((unsigned long)s < PAGE_SIZE)
> - s = "(null)";
> + s = BAD_PTR_STRING(s);
It doesn't make any sense before your patch 2.
> if ((unsigned long)dn < PAGE_SIZE)
> - return string(buf, end, "(null)", spec);
> + return string(buf, end, BAD_PTR_STRING(dn), spec);
It simple doesn't make sense.
The idea is to do it below, in the pointer.
These certain lines are going to be removed by my patch.
> - return string(buf, end, "(null)", spec);
> + return string(buf, end, BAD_PTR_STRING(ptr), spec);
Doesn't make sense before your patch 2.
> if ((unsigned long)save_str > (unsigned
> long)-PAGE_SIZE
> || (unsigned long)save_str <
> PAGE_SIZE)
> - save_str = "(null)";
> + save_str = BAD_PTR_STRING(save_str);
This is perhaps one valid change in such situation.
--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy
next prev parent reply other threads:[~2018-03-07 13:17 UTC|newest]
Thread overview: 89+ 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
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 ` Andy Shevchenko [this message]
2018-03-07 13:42 ` [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs 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
2018-03-06 18:22 [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs Alexey Dobriyan
2018-03-06 18:42 ` Adam Borowski
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