From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Petr Mladek <pmladek@suse.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"Tobin C . Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
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>,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH v5 03/11] vsprintf: Consistent %pK handling for kptr_restrict == 0
Date: Wed, 25 Apr 2018 17:58:41 +0300 [thread overview]
Message-ID: <1524668321.21176.560.camel@linux.intel.com> (raw)
In-Reply-To: <20180425111251.13246-4-pmladek@suse.com>
On Wed, 2018-04-25 at 13:12 +0200, Petr Mladek wrote:
> restricted_pointer() pretends that it prints the address when
> kptr_restrict
> is set to zero. But it is never called in this situation. Instead,
> pointer() falls back to ptr_to_id() and hashes the pointer.
>
> This patch removes the potential confusion. klp_restrict is checked
> only
> in restricted_pointer().
>
> It actually fixes a small race when the address might get printed
> unhashed:
>
> CPU0 CPU1
>
> pointer()
> if (!kptr_restrict)
> /* for example set to 2 */
> restricted_pointer()
> /* echo 0
> >/proc/sys/kernel/kptr_restrict */
> proc_dointvec_minmax_sysadmin()
> klpr_restrict = 0;
> switch(kptr_restrict)
> case 0:
> break:
>
> number()
>
FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Fixes: commit ef0010a30935de4e0211 ("vsprintf: don't use
> 'restricted_pointer()' when not restricting")
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Tobin Harding <me@tobin.cc>
> Cc: Kees Cook <keescook@chromium.org>
> Signed-off-by: Petr Mladek <pmladek@suse.com>
> ---
> lib/vsprintf.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index eef9f725e9ff..2678dfe61d73 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -694,8 +694,8 @@ char *restricted_pointer(char *buf, char *end,
> const void *ptr,
> {
> switch (kptr_restrict) {
> case 0:
> - /* Always print %pK values */
> - break;
> + /* Handle as %p, hash and do _not_ leak addresses. */
> + return ptr_to_id(buf, end, ptr, spec);
> case 1: {
> const struct cred *cred;
>
> @@ -1915,8 +1915,6 @@ char *pointer(const char *fmt, char *buf, char
> *end, void *ptr,
> return buf;
> }
> case 'K':
> - if (!kptr_restrict)
> - break;
> return restricted_pointer(buf, end, ptr, spec);
> case 'N':
> return netdev_bits(buf, end, ptr, fmt);
--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy
next prev parent reply other threads:[~2018-04-25 14:58 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-25 11:12 [PATCH v5 00/11] vsprintf: Prevent silent crashes and consolidate error handling Petr Mladek
2018-04-25 11:12 ` [PATCH v5 01/11] vsprintf: Shuffle misc pointer to string functions Petr Mladek
2018-04-25 14:57 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 02/11] vsprintf: Add missing const ptr qualifier to prt_to_id() Petr Mladek
2018-04-25 14:57 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 03/11] vsprintf: Consistent %pK handling for kptr_restrict == 0 Petr Mladek
2018-04-25 14:58 ` Andy Shevchenko [this message]
2018-04-25 11:12 ` [PATCH v5 04/11] vsprintf: Do not check address of well-known strings Petr Mladek
2018-04-25 11:44 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 05/11] vsprintf: Consolidate handling of unknown pointer specifiers Petr Mladek
2018-04-25 13:08 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 06/11] vsprintf: Factor out %p[iI] handler as ip_addr_string() Petr Mladek
2018-04-25 13:11 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 07/11] vsprintf: Factor out %pV handler as va_format() Petr Mladek
2018-04-25 14:56 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 08/11] vsprintf: Factor out %pO handler as kobject_string() Petr Mladek
2018-04-25 15:01 ` Andy Shevchenko
2018-04-25 11:12 ` [PATCH v5 09/11] vsprintf: Prevent crash when dereferencing invalid pointers Petr Mladek
2018-04-25 15:10 ` Andy Shevchenko
2018-04-25 15:32 ` Andy Shevchenko
2018-04-27 12:47 ` Petr Mladek
2018-05-03 11:55 ` Andy Shevchenko
2018-04-26 21:46 ` kbuild test robot
2018-04-25 11:12 ` [PATCH v5 10/11] vsprintf: WARN() on invalid pointer access Petr Mladek
2018-04-25 12:43 ` Rasmus Villemoes
2018-04-26 1:28 ` Sergey Senozhatsky
2018-04-27 12:37 ` Petr Mladek
2018-04-25 11:12 ` [PATCH v5 11/11] vsprintf: Avoid confusion between invalid address and value Petr Mladek
2018-04-27 14:10 ` [PATCH v5 00/11] vsprintf: Prevent silent crashes and consolidate error handling Petr Mladek
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=1524668321.21176.560.camel@linux.intel.com \
--to=andriy.shevchenko@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=joe@perches.com \
--cc=keescook@chromium.org \
--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).