On 25.04.22 15:27, Miaohe Lin wrote:
> rcu_read_lock is required by grabbing the task refcount but it's not
> needed for ptrace_may_access. So we could release the rcu lock after
> task refcount is successfully grabbed to reduce the rcu holding time.
>
> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: David Howells <dhowells@xxxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> ---
> mm/migrate.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index b2678279eb43..b779646665fe 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1902,17 +1902,16 @@ static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
> return ERR_PTR(-ESRCH);
> }
> get_task_struct(task);
> + rcu_read_unlock();
>
> /*
> * Check if this process has the right to modify the specified
> * process. Use the regular "ptrace_may_access()" checks.
> */
> if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
> - rcu_read_unlock();
> mm = ERR_PTR(-EPERM);
> goto out;
> }
> - rcu_read_unlock();
>
> mm = ERR_PTR(security_task_movememory(task));
> if (IS_ERR(mm))
Similar pattern in:
mm/mempolicy.c:kernel_migrate_pages()
kernel/futex/syscalls.c:get_robust_list()
kernel/nsproxy.c:validate_nsset()
Exception:
sched/core_sched.c:sched_core_share_pid()
Should we unify -- i.e., adjust the remaining 3 as well?
--
Thanks,
David / dhildenb
