Messages in this thread | | | From | Madhuparna Bhowmik <> | Date | Thu, 6 Feb 2020 16:30:51 +0530 | Subject | Re: [PATCH] signal.c: Fix sparse warnings |
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On Wed, Feb 05, 2020 at 04:59:52PM -0600, Eric W. Biederman wrote: > madhuparnabhowmik10@gmail.com writes: > > > From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com> > > > > This patch fixes the following two sparse warnings caused due to > > accessing RCU protected pointer tsk->parent without rcu primitives. > > > > kernel/signal.c:1948:65: warning: incorrect type in argument 1 (different address spaces) > > kernel/signal.c:1948:65: expected struct task_struct *tsk > > kernel/signal.c:1948:65: got struct task_struct [noderef] <asn:4> *parent > > kernel/signal.c:1949:40: warning: incorrect type in argument 1 (different address spaces) > > kernel/signal.c:1949:40: expected void const volatile *p > > kernel/signal.c:1949:40: got struct cred const [noderef] <asn:4> *[noderef] <asn:4> * > > kernel/signal.c:1949:40: warning: incorrect type in argument 1 (different address spaces) > > kernel/signal.c:1949:40: expected void const volatile *p > > kernel/signal.c:1949:40: got struct cred const [noderef] <asn:4> *[noderef] <asn:4> * > > > > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com> > > --- > > kernel/signal.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/signal.c b/kernel/signal.c > > index 9ad8dea93dbb..8227058ea8c4 100644 > > --- a/kernel/signal.c > > +++ b/kernel/signal.c > > @@ -1945,8 +1945,8 @@ bool do_notify_parent(struct task_struct *tsk, int sig) > > * correct to rely on this > > */ > > rcu_read_lock(); > > - info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(tsk->parent)); > > - info.si_uid = from_kuid_munged(task_cred_xxx(tsk->parent, user_ns), > > + info.si_pid = task_pid_nr_ns(tsk, task_active_pid_ns(rcu_dereference(tsk->parent))); > > + info.si_uid = from_kuid_munged(task_cred_xxx(rcu_dereference(tsk->parent), user_ns), > > task_uid(tsk)); > > rcu_read_unlock(); > > > Still wrong because that access fundamentally depends upon the > task_list_lock no the rcu_read_lock. Things need to be consistent for > longer than the rcu_read_lock is held. > Okay, then how about something like rcu_dereference_protected(tsk->parent, lockdep_is_held(&tasklist_lock))? Let me know if this looks fine to you.
Thank you, Madhuparna
> This patch makes sparse happy and confuses programmers who are trying to > read the code. > > > Eric
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