lkml.org 
[lkml]   [2018]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v5 03/11] vsprintf: Consistent %pK handling for kptr_restrict == 0
    From
    Date
    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 <andriy.shevchenko@linux.intel.com>

    > 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>
    > ---
    > 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 <andriy.shevchenko@linux.intel.com>
    Intel Finland Oy

    \
     
     \ /
      Last update: 2018-04-25 16:59    [W:4.154 / U:0.104 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site