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 should actually fix 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 <torva...@linux-foundation.org>
Cc: Tobin Harding <m...@tobin.cc>
Cc: Kees Cook <keesc...@chromium.org>
Signed-off-by: Petr Mladek <pmla...@suse.com>
---
 lib/vsprintf.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c0c677c6a833..9ade2c4f21ba 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -637,7 +637,8 @@ static int __init initialize_ptr_random(void)
 early_initcall(initialize_ptr_random);
 
 /* Maps a pointer to a 32 bit unique identifier. */
-static char *ptr_to_id(char *buf, char *end, void *ptr, struct printf_spec 
spec)
+static char *ptr_to_id(char *buf, char *end,
+                      const void *ptr, struct printf_spec spec)
 {
        unsigned long hashval;
        const int default_width = 2 * sizeof(ptr);
@@ -1426,8 +1427,8 @@ 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;
 
@@ -1931,8 +1932,6 @@ 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

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