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 <[email protected]> > Fixes: commit ef0010a30935de4e0211 ("vsprintf: don't use > 'restricted_pointer()' when not restricting") > Cc: Linus Torvalds <[email protected]> > Cc: Tobin Harding <[email protected]> > Cc: Kees Cook <[email protected]> > Signed-off-by: Petr Mladek <[email protected]> > --- > 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 <[email protected]> Intel Finland Oy
