Commit 4dc200ce authored by Miaohe Lin's avatar Miaohe Lin Committed by Linus Torvalds

mm/migrate: avoid possible unnecessary process right check in kernel_move_pages()

There is no need to check if this process has the right to modify the
specified process when they are same.  And we could also skip the security
hook call if a process is modifying its own pages.  Add helper function to
handle these.
Suggested-by: default avatarMatthew Wilcox <willy@infradead.org>
Signed-off-by: default avatarHongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Christopher Lameter <cl@linux.com>
Link: https://lkml.kernel.org/r/20200819083331.19012-1-linmiaohe@huawei.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 203e6e5c
...@@ -1864,33 +1864,27 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, ...@@ -1864,33 +1864,27 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
return nr_pages ? -EFAULT : 0; return nr_pages ? -EFAULT : 0;
} }
/* static struct mm_struct *find_mm_struct(pid_t pid, nodemask_t *mem_nodes)
* Move a list of pages in the address space of the currently executing
* process.
*/
static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{ {
struct task_struct *task; struct task_struct *task;
struct mm_struct *mm; struct mm_struct *mm;
int err;
nodemask_t task_nodes;
/* Check flags */
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
return -EINVAL;
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) /*
return -EPERM; * There is no need to check if current process has the right to modify
* the specified process when they are same.
*/
if (!pid) {
mmget(current->mm);
*mem_nodes = cpuset_mems_allowed(current);
return current->mm;
}
/* Find the mm_struct */ /* Find the mm_struct */
rcu_read_lock(); rcu_read_lock();
task = pid ? find_task_by_vpid(pid) : current; task = find_task_by_vpid(pid);
if (!task) { if (!task) {
rcu_read_unlock(); rcu_read_unlock();
return -ESRCH; return ERR_PTR(-ESRCH);
} }
get_task_struct(task); get_task_struct(task);
...@@ -1900,22 +1894,47 @@ static int kernel_move_pages(pid_t pid, unsigned long nr_pages, ...@@ -1900,22 +1894,47 @@ static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
*/ */
if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
rcu_read_unlock(); rcu_read_unlock();
err = -EPERM; mm = ERR_PTR(-EPERM);
goto out; goto out;
} }
rcu_read_unlock(); rcu_read_unlock();
err = security_task_movememory(task); mm = ERR_PTR(security_task_movememory(task));
if (err) if (IS_ERR(mm))
goto out; goto out;
*mem_nodes = cpuset_mems_allowed(task);
task_nodes = cpuset_mems_allowed(task);
mm = get_task_mm(task); mm = get_task_mm(task);
out:
put_task_struct(task); put_task_struct(task);
if (!mm) if (!mm)
mm = ERR_PTR(-EINVAL);
return mm;
}
/*
* Move a list of pages in the address space of the currently executing
* process.
*/
static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
const void __user * __user *pages,
const int __user *nodes,
int __user *status, int flags)
{
struct mm_struct *mm;
int err;
nodemask_t task_nodes;
/* Check flags */
if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
return -EINVAL; return -EINVAL;
if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE))
return -EPERM;
mm = find_mm_struct(pid, &task_nodes);
if (IS_ERR(mm))
return PTR_ERR(mm);
if (nodes) if (nodes)
err = do_pages_move(mm, task_nodes, nr_pages, pages, err = do_pages_move(mm, task_nodes, nr_pages, pages,
nodes, status, flags); nodes, status, flags);
...@@ -1924,10 +1943,6 @@ static int kernel_move_pages(pid_t pid, unsigned long nr_pages, ...@@ -1924,10 +1943,6 @@ static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
mmput(mm); mmput(mm);
return err; return err;
out:
put_task_struct(task);
return err;
} }
SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
......
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