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From: Petr Mladek <pmladek@suse.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.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, Petr Mladek <pmladek@suse.com>,
	Kees Cook <keescook@chromium.org>
Subject: [PATCH v5 03/11] vsprintf: Consistent %pK handling for kptr_restrict == 0
Date: Wed, 25 Apr 2018 13:12:43 +0200	[thread overview]
Message-ID: <20180425111251.13246-4-pmladek@suse.com> (raw)
In-Reply-To: <20180425111251.13246-1-pmladek@suse.com>

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()

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);
-- 
2.13.6

  parent reply	other threads:[~2018-04-25 11:16 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 ` Petr Mladek [this message]
2018-04-25 14:58   ` [PATCH v5 03/11] vsprintf: Consistent %pK handling for kptr_restrict == 0 Andy Shevchenko
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

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