linux-kernel - [PATCH] seq_file: fix passing wrong private data

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Message-Id: <20211029032638.84884-1-songmuchun@bytedance.com>
Date:   Fri, 29 Oct 2021 11:26:38 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     andriy.shevchenko@...ux.intel.com, akpm@...ux-foundation.org,
        sfr@...b.auug.org.au, revest@...omium.org, adobriyan@...il.com
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] seq_file: fix passing wrong private data

DEFINE_PROC_SHOW_ATTRIBUTE() is supposed to be used to define a series
of functions and variables to register proc file easily. And the users
can use proc_create_data() to pass their own private data and get it
via seq->private in the callback. Unfortunately, the proc file system
use PDE_DATA() to get private data instead of inode->i_private. So fix
it. Fortunately, there only one user of it which does not pass any
private data, so this bug does not break any in-tree codes.

Fixes: 97a32539b956 ("proc: convert everything to "struct proc_ops"")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 include/linux/seq_file.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 103776e18555..72dbb44a4573 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -209,7 +209,7 @@ static const struct file_operations __name ## _fops = {			\
 #define DEFINE_PROC_SHOW_ATTRIBUTE(__name)				\
 static int __name ## _open(struct inode *inode, struct file *file)	\
 {									\
-	return single_open(file, __name ## _show, inode->i_private);	\
+	return single_open(file, __name ## _show, PDE_DATA(inode));	\
 }									\
 									\
 static const struct proc_ops __name ## _proc_ops = {			\
-- 
2.11.0