)
On Wed, Jan 12, 2022 at 6:40 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
>
> On Tue, Jan 11, 2022 at 03:23:09PM -0800, Suren Baghdasaryan wrote:
> > With write operation on psi files replacing old trigger with a new one,
> > the lifetime of its waitqueue is totally arbitrary. Overwriting an
> > existing trigger causes its waitqueue to be freed and pending poll()
> > will stumble on trigger->event_wait which was destroyed.
> > Fix this by disallowing to redefine an existing psi trigger. If a write
> > operation is used on a file descriptor with an already existing psi
> > trigger, the operation will fail with EBUSY error.
> > Also bypass a check for psi_disabled in the psi_trigger_destroy as the
> > flag can be flipped after the trigger is created, leading to a memory
> > leak.
> >
> > Fixes: 0e94682b73bf ("psi: introduce psi monitor")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reported-by: syzbot+cdb5dd11c97cc532efad@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Analyzed-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
>
> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Hmm. kernel test robot notified me of new (which are not really new)
warnings but I don't think this patch specifically introduced them:
kernel/sched/psi.c:1112:21: warning: no previous prototype for
function 'psi_trigger_create' [-Wmissing-prototypes]
struct psi_trigger *psi_trigger_create(struct psi_group *group,
^
kernel/sched/psi.c:1112:1: note: declare 'static' if the function
is not intended to be used outside of this translation unit
struct psi_trigger *psi_trigger_create(struct psi_group *group,
^
static
>> kernel/sched/psi.c:1182:6: warning: no previous prototype for function 'psi_trigger_destroy' [-Wmissing-prototypes]
void psi_trigger_destroy(struct psi_trigger *t)
^
kernel/sched/psi.c:1182:1: note: declare 'static' if the function
is not intended to be used outside of this translation unit
void psi_trigger_destroy(struct psi_trigger *t)
^
static
kernel/sched/psi.c:1249:10: warning: no previous prototype for
function 'psi_trigger_poll' [-Wmissing-prototypes]
__poll_t psi_trigger_poll(void **trigger_ptr,
^
kernel/sched/psi.c:1249:1: note: declare 'static' if the function
is not intended to be used outside of this translation unit
__poll_t psi_trigger_poll(void **trigger_ptr,
^
This happens with the following config:
CONFIG_CGROUPS=n
CONFIG_PSI=y
With cgroups disabled these functions are defined as non-static but
are not defined in the header
(https://elixir.bootlin.com/linux/latest/source/include/linux/psi.h#L28)
since the only external user cgroup.c is disabled. The cleanest way to
fix these I think is by doing smth like this in psi.c:
struct psi_trigger *_psi_trigger_create(struct psi_group *group, char
*buf, size_t nbytes, enum psi_res res)
{
// original psi_trigger_create code
}
#ifdef CONFIG_CGROUPS
struct psi_trigger *psi_trigger_create(struct psi_group *group, char
*buf, size_t nbytes, enum psi_res res)
{
return _psi_trigger_create(group, buf, nbytes, res);
}
#else
static struct psi_trigger *psi_trigger_create(struct psi_group *group,
char *buf, size_t nbytes, enum psi_res res)
{
return _psi_trigger_create(group, buf, nbytes, res);
}
#endif
Two questions:
1. Is this even worth fixing?
2. If so, I would like to do that as a separate patch (these warnings
are unrelated to the changes in this patch). Would that be ok?
Thanks,
Suren.
