linux-kernel - [PATCH] mm/migrate: Avoid possible unnecessary ptrace_may_access() call in kernel_move

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Date:   Mon, 17 Aug 2020 07:59:33 -0400
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm/migrate: Avoid possible unnecessary ptrace_may_access() call 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.

Signed-off-by: Hongxiang Lou <louhongxiang@...wei.com>
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 34a842a8eb6a..342c1ce0b433 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1903,7 +1903,7 @@ static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
 	 * 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)) {
+	if (pid && !ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
 		rcu_read_unlock();
 		err = -EPERM;
 		goto out;
-- 
2.19.1