linux-kernel - [PATCH] fs/proc: Fix NULL pointer dereference in pid_delete

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Date:   Wed,  9 Dec 2020 19:21:00 +0800
From:   Yahu Gao <yahu.gao@...driver.com>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        yahu.gao@...driver.com
Subject: [PATCH] fs/proc: Fix NULL pointer dereference in pid_delete_dentry

Get the staus of task from the pointer of proc inode directly is not
safe. The function get_proc_task make it happen in RCU protection.

Signed-off-by: Yahu Gao <yahu.gao@...driver.com>
---
 fs/proc/base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1bc9bcdef09f..05f33bb35067 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1994,7 +1994,7 @@ static int pid_revalidate(struct dentry *dentry, unsigned int flags)
 
 static inline bool proc_inode_is_dead(struct inode *inode)
 {
-	return !proc_pid(inode)->tasks[PIDTYPE_PID].first;
+	return !get_proc_task(inode);
 }
 
 int pid_delete_dentry(const struct dentry *dentry)
-- 
2.25.1