[PATCH] ramfs: skip mknod if inode already exists.

[PATCH] ramfs: skip mknod if inode already exists.

[Chen Li]

It's possible we try to mknod a dentry, which have
already bound to an inode, just skip it.

Signed-off-by: Chen Li <chenli@uniontech.com>
---
 fs/ramfs/inode.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 9ebd17d7befb..6cb1de521142 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -106,6 +106,8 @@ ramfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 {
 	struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
 	int error = -ENOSPC;
+	if (dentry->d_inode)
+		return -EEXIST;
 
 	if (inode) {
 		d_instantiate(dentry, inode);
-- 
2.32.0

Re: [PATCH] ramfs: skip mknod if inode already exists.

[Christoph Hellwig]

On Wed, Jun 16, 2021 at 10:53:12AM +0800, Chen Li wrote:
> 
> It's possible we try to mknod a dentry, which have
> already bound to an inode, just skip it.

How do you think this could happen?

Re: [PATCH] ramfs: skip mknod if inode already exists.【请注意，邮件由batv+ae8989e1668f84a74d37+6506+infradead.org+hch@casper.srs.infradead.org代发】

[Chen Li]

On Wed, 16 Jun 2021 13:10:25 +0800,
Christoph Hellwig wrote:
> 
> On Wed, Jun 16, 2021 at 10:53:12AM +0800, Chen Li wrote:
> > 
> > It's possible we try to mknod a dentry, which have
> > already bound to an inode, just skip it.
> 
> How do you think this could happen?
> 
> 

Sorry, that's my bad. I noticed unionfs used to do this check in 9c5b4452998c6e670cfde0928b277e9c50d9a676, but not sure is it a must.

Re: [PATCH] ramfs: skip mknod if inode already exists.

[Al Viro]

On Wed, Jun 16, 2021 at 10:53:12AM +0800, Chen Li wrote:
> 
> It's possible we try to mknod a dentry, which have
> already bound to an inode, just skip it.

Caller should have checked may_create(), which includes EEXIST handling.
NAKed-by: Al Viro <viro@zeniv.linux.org.uk>

Incidentally, if it ever had been called that way, your variant would
leak inode.  Not the main problem, though...

Re: [PATCH] ramfs: skip mknod if inode already exists.【请注意，邮件由viro@ftp.linux.org.uk代发】

[Chen Li]

On Wed, 16 Jun 2021 20:16:58 +0800,
Al Viro wrote:
> 
> On Wed, Jun 16, 2021 at 10:53:12AM +0800, Chen Li wrote:
> > 
> > It's possible we try to mknod a dentry, which have
> > already bound to an inode, just skip it.
> 
> Caller should have checked may_create(), which includes EEXIST handling.
> NAKed-by: Al Viro <viro@zeniv.linux.org.uk>

Don't know may_create before, thanks!
> 
> Incidentally, if it ever had been called that way, your variant would
> leak inode.  Not the main problem, though...
> 
>