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But > this is not safe in general since the group leader could change when a > task exits. See for example commit a15f37a40145c ("kernel/sys.c: fix the > racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths"). > > All existing users of Task::group_leader() call this method on current, > which is guaranteed running, so there's not an actual issue in Rust code > today. But to prevent code in the future from making this mistake, > restrict Task::group_leader() so that it can only be called on current. > > There are some other cases where accessing task->group_leader is okay. > For example it can be safe if you hold tasklist_lock or rcu_read_lock(). > However, only supporting current->group_leader is sufficient for all > in-tree Rust users of group_leader right now. Safe Rust functionality > for accessing it under rcu or while holding tasklist_lock may be added > in the future if required by any future Rust module. > > Reported-by: Oleg Nesterov > Closes: https://lore.kernel.org/all/aTLnV-5jlgfk1aRK@redhat.com/ > Fixes: 313c4281bc9d ("rust: add basic `Task`") > Cc: stable@vger.kernel.org > Signed-off-by: Alice Ryhl Reviewed-by: Gary Guo > --- > rust/kernel/task.rs | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-)