On Wed, Dec 10, 2014 at 11:11:47AM +0100, Petr Mladek wrote:
> On Tue 2014-12-09 12:32:49, Josh Poimboeuf wrote:
> > On Tue, Dec 09, 2014 at 07:05:02PM +0100, Petr Mladek wrote:
> > > klp_patch_enable() and klp_patch_disable() should check the current state
> > > of the patch under the klp_lock. Otherwise, it might detect that the operation
> > > is valid but the situation might change before it takes the lock.
> >
> > Hi Petr,
> >
> > Thanks for the patches.
> >
> > I don't think this patch is necessary. klp_is_enabled() doesn't check
> > the state of the patch. It checks the initialization state of the core
> > module (klp_root_kobj), which can only be set in klp_init(). It's not
> > protected by the lock, so I don't see the point of this patch.
>
> Ah, I have misread the name and expected that it checked whether
> the patch was enabled or disabled. The original code is OK then.
>
> Well, Jiri Kosina pointed out that the check did not make much sense.
> klp_is_enabled() could not be called if the livepatch module is not
> loaded. And the later check for klp_patch_is_registered() is enough
> to check whether the klp_enable_patch()/klp_disable_patch() calls
> are allowed or not.
But livepatch isn't a module, it's part of the kernel. Even if the init
function returns an error, that doesn't prevent any of the other
exported functions from getting called.
>
> So, I suggest to remove the checks at all.
>
> Best Regards,
> Petr
>
>
> > >
> > > Signed-off-by: Petr Mladek <pmladek@xxxxxxx>
> > > ---
> > > kernel/livepatch/core.c | 16 ++++++++++------
> > > 1 file changed, 10 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > > index d6d0f50e81f8..b848069e44cc 100644
> > > --- a/kernel/livepatch/core.c
> > > +++ b/kernel/livepatch/core.c
> > > @@ -425,11 +425,13 @@ int klp_disable_patch(struct klp_patch *patch)
> > > {
> > > int ret;
> > >
> > > - if (!klp_is_enabled())
> > > - return -ENODEV;
> > > -
> > > mutex_lock(&klp_mutex);
> > >
> > > + if (!klp_is_enabled()) {
> > > + ret = -ENODEV;
> > > + goto err;
> > > + }
> > > +
> > > if (!klp_patch_is_registered(patch)) {
> > > ret = -EINVAL;
> > > goto err;
> > > @@ -489,11 +491,13 @@ int klp_enable_patch(struct klp_patch *patch)
> > > {
> > > int ret;
> > >
> > > - if (!klp_is_enabled())
> > > - return -ENODEV;
> > > -
> > > mutex_lock(&klp_mutex);
> > >
> > > + if (!klp_is_enabled()) {
> > > + ret = -ENODEV;
> > > + goto err;
> > > + }
> > > +
> > > if (!klp_patch_is_registered(patch)) {
> > > ret = -EINVAL;
> > > goto err;
> > > --
> > > 1.8.5.2
> > >
> >
> > --
> > Josh
--
Josh
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