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 v7 02/10] vsprintf: Consistent %pK handling for kptr_restrict == 0
Date: Wed, 17 Apr 2019 13:53:42 +0200 [thread overview]
Message-ID: <20190417115350.20479-3-pmladek@suse.com> (raw)
In-Reply-To: <20190417115350.20479-1-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>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
lib/vsprintf.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index eb7b4a06e1f0..2af48948a973 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -725,8 +725,8 @@ 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;
@@ -2041,8 +2041,6 @@ 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, spec, fmt);
--
2.16.4
next prev parent reply other threads:[~2019-04-17 11:55 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-17 11:53 [PATCH v7 00/10] vsprintf: Prevent silent crashes and consolidate error handling Petr Mladek
2019-04-17 11:53 ` [PATCH v7 01/10] vsprintf: Shuffle restricted_pointer() Petr Mladek
2019-04-17 11:53 ` Petr Mladek [this message]
2019-04-17 13:44 ` [PATCH v7 02/10] vsprintf: Consistent %pK handling for kptr_restrict == 0 Steven Rostedt
2019-04-17 11:53 ` [PATCH v7 03/10] vsprintf: Do not check address of well-known strings Petr Mladek
2019-04-17 11:53 ` [PATCH v7 04/10] vsprintf: Factor out %p[iI] handler as ip_addr_string() Petr Mladek
2019-04-17 11:53 ` [PATCH v7 05/10] vsprintf: Factor out %pV handler as va_format() Petr Mladek
2019-04-17 11:53 ` [PATCH v7 06/10] vsprintf: Factor out %pO handler as kobject_string() Petr Mladek
2019-04-17 11:53 ` [PATCH v7 07/10] vsprintf: Consolidate handling of unknown pointer specifiers Petr Mladek
2019-04-18 14:34 ` Sergey Senozhatsky
2019-04-18 14:43 ` Sergey Senozhatsky
2019-04-18 14:50 ` Sergey Senozhatsky
2019-06-25 10:59 ` Geert Uytterhoeven
2019-06-26 10:46 ` Petr Mladek
2019-06-26 11:16 ` Geert Uytterhoeven
2019-04-17 11:53 ` [PATCH v7 08/10] vsprintf: Prevent crash when dereferencing invalid pointers Petr Mladek
2019-04-17 11:53 ` [PATCH v7 09/10] vsprintf: Avoid confusion between invalid address and value Petr Mladek
2019-04-17 11:53 ` [PATCH v7 10/10] vsprintf: Limit the length of inlined error messages Petr Mladek
2019-04-19 1:51 ` [PATCH v7 00/10] vsprintf: Prevent silent crashes and consolidate error handling Sergey Senozhatsky
2019-04-24 13:53 ` Petr Mladek
2019-04-26 13:02 ` Andy Shevchenko
2019-04-26 14:27 ` Petr Mladek
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