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From: Chengguang Xu <cgxu519@mykernel.net>
To: miklos@szeredi.hu
Cc: linux-unionfs@vger.kernel.org, Chengguang Xu <cgxu519@mykernel.net>
Subject: [RFC PATCH 2/2] ovl: enhance write permission check for writable open
Date: Sat, 24 Apr 2021 22:03:16 +0800	[thread overview]
Message-ID: <20210424140316.485444-2-cgxu519@mykernel.net> (raw)
In-Reply-To: <20210424140316.485444-1-cgxu519@mykernel.net>

Check upper file's write permission when open on writable mode.

NOTE: lower files may be shared between differnt overlayfs instances,
so we skip the check of lower file to avoid introducing interferes.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
 fs/overlayfs/file.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 6e454a294046..1c3c24d07d01 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -144,12 +144,18 @@ static int ovl_real_fdget(const struct file *file, struct fd *real)
 static int ovl_open(struct inode *inode, struct file *file)
 {
 	struct file *realfile;
+	struct inode *upperinode;
 	int err;
 
 	err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
 	if (err)
 		return err;
 
+	upperinode = ovl_inode_upper(inode);
+	if (((file->f_mode & FMODE_WRITE) || file->f_flags & O_TRUNC) &&
+	    (upperinode && atomic_read(&upperinode->i_writecount) < 0))
+		return -ETXTBSY;
+
 	/* No longer need these flags, so don't pass them on to underlying fs */
 	file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
-- 
2.27.0



  reply	other threads:[~2021-04-24 14:06 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-24 14:03 [RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-04-24 14:03 ` Chengguang Xu [this message]
2021-07-21 13:14   ` [RFC PATCH 2/2] ovl: enhance write permission check for writable open Miklos Szeredi
2021-04-28 12:18 ` 回复:[RFC PATCH 1/2] ovl: skip checking lower file's write permisson on truncate Chengguang Xu
2021-07-20 14:35 ` [RFC " Miklos Szeredi
2021-07-20 15:19   ` Miklos Szeredi
2021-07-20 16:01     ` Chengguang Xu
2021-07-20 16:01     ` Miklos Szeredi
2021-07-20 16:04       ` Chengguang Xu

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