vsprintf: Consistent %pK handling for kptr_restrict == 0
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: ef0010a30935de4e0211 ("vsprintf: don't use 'restricted_pointer()' when not restricting")
Link: http://lkml.kernel.org/r/20190417115350.20479-3-pmladek@suse.com
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index eb7b4a0..2af4894 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);