On Wed, Aug 19, 2020 at 10:06:55PM +0200, Luc Van Oostenryck wrote:
> On Wed, Aug 19, 2020 at 12:15:46PM -0700, Randy Dunlap wrote:
> > On Linux kernel tree v5.9-rc1, with sparse v0.6.2-180-g49f7e13a,
> > I see this sparse warning which I don't grok:
> >
> > ../include/uapi/asm-generic/signal-defs.h:19:29: CK: error: multiple address spaces given
> >
> > for this source code:
> >
> > typedef void __signalfn_t(int);
> > typedef __signalfn_t __user *__sighandler_t; <<<<< line 19
> >
> > Are there multiple address spaces there? What are they?
> >
> >
> >
> > or: is the warning related to the other nearby warnings? (e.g.:)
> >
> > ../kernel/signal.c:541:53: CK: warning: incorrect type in initializer (different address spaces)
> > ../kernel/signal.c:541:53: CK: expected struct k_sigaction *ka
> > ../kernel/signal.c:541:53: CK: got struct k_sigaction [noderef] __rcu *
> > ../include/uapi/asm-generic/signal-defs.h:19:29: CK: error: multiple address spaces given
> > ../kernel/signal.c:694:33: CK: warning: incorrect type in argument 1 (different address spaces)
> > ../kernel/signal.c:694:33: CK: expected struct spinlock [usertype] *lock
> > ../kernel/signal.c:694:33: CK: got struct spinlock [noderef] __rcu *
>
> I would guess that this __sighandler_t is used somewhere in a
> struct which is itself accessed via a __rcu pointer.
> But that would not explain the level of dereference.
>
> I'll need to check this one.
The location of the warning should be the assignment in kernel/signal.c:69
static void __user *sig_handler(struct task_struct *t, int sig)
{
return t->sighand->action[sig - 1].sa.sa_handler;
}
There is a lot of type abuses in this file, between 'void __user *' and
__sighandler_t, but the root cause of the warning is the '__rcu' in
struct task_struct {
...
struct sighand_struct __rcu *sighand;
...
}
Best regards,
-- Luc
