Messages in this thread | | | Date | Wed, 17 Apr 2019 09:44:30 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v7 02/10] vsprintf: Consistent %pK handling for kptr_restrict == 0 |
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On Wed, 17 Apr 2019 13:53:42 +0200 Petr Mladek <pmladek@suse.com> 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() > > 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>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
-- Steve
> --- > 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);
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