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SubjectRe: [PATCH] signal.c: Fix sparse warnings
On Wed, Feb 05, 2020 at 09:53:19PM +0530, madhuparnabhowmik10@gmail.com wrote:
> 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..3d59e5652d94 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_access_pointer(tsk->parent)));
> + info.si_uid = from_kuid_munged(task_cred_xxx(rcu_access_pointer(tsk->parent), user_ns),

Shouldn't rcu_dereference() OR rcu_dereference_check() be better suited
here? Since, rcu_access_pointer() omits all lockdep checks.

Thanks
Amol

> task_uid(tsk));
> rcu_read_unlock();
>
> --
> 2.17.1
>

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