[PATCH 5.10 120/770] kcmp: In get_file_raw_ptr use task_lookup_fd_rcu

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>

[ Upstream commit ed77e80e14a3cd55c73848b9e8043020e717ce12 ]

Modify get_file_raw_ptr to use task_lookup_fd_rcu.  The helper
task_lookup_fd_rcu does the work of taking the task lock and verifying
that task->files != NULL and then calls files_lookup_fd_rcu.  So let
use the helper to make a simpler implementation of get_file_raw_ptr.

Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20201120231441.29911-13-ebiederm@xxxxxxxxxxxx
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/kcmp.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index 5b2435e030472..5353edfad8e11 100644
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -61,16 +61,11 @@ static int kcmp_ptr(void *v1, void *v2, enum kcmp_type type)
 static struct file *
 get_file_raw_ptr(struct task_struct *task, unsigned int idx)
 {
-	struct file *file = NULL;
+	struct file *file;
 
-	task_lock(task);
 	rcu_read_lock();
-
-	if (task->files)
-		file = files_lookup_fd_rcu(task->files, idx);
-
+	file = task_lookup_fd_rcu(task, idx);
 	rcu_read_unlock();
-	task_unlock(task);
 
 	return file;
 }
-- 
2.43.0







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