ACK: [D][SRU][PATCH 1/1] ovl: do not generate duplicate fsnotify events for "fake" path

[Stefan Bader]

On 17.06.19 13:04, Po-Hsu Lin wrote:
> From: Amir Goldstein <amir73il at gmail.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1833028
> 
> Overlayfs "fake" path is used for stacked file operations on underlying
> files.  Operations on files with "fake" path must not generate fsnotify
> events with path data, because those events have already been generated at
> overlayfs layer and because the reported event->fd for fanotify marks on
> underlying inode/filesystem will have the wrong path (the overlayfs path).
> 
> Link: https://lore.kernel.org/linux-fsdevel/20190423065024.12695-1-jencce.kernel@gmail.com/
> Reported-by: Murphy Zhou <jencce.kernel at gmail.com>
> Fixes: d1d04ef8572b ("ovl: stack file ops")
> Signed-off-by: Amir Goldstein <amir73il at gmail.com>
> Signed-off-by: Miklos Szeredi <mszeredi at redhat.com>
> (cherry picked from commit d989903058a83e8536cc7aadf9256a47d5c173fe)
> Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  fs/overlayfs/file.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index 84dd957..6f6eb63 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -29,10 +29,11 @@ static struct file *ovl_open_realfile(const struct file *file,
>  	struct inode *inode = file_inode(file);
>  	struct file *realfile;
>  	const struct cred *old_cred;
> +	int flags = file->f_flags | O_NOATIME | FMODE_NONOTIFY;
>  
>  	old_cred = ovl_override_creds(inode->i_sb);
> -	realfile = open_with_fake_path(&file->f_path, file->f_flags | O_NOATIME,
> -				       realinode, current_cred());
> +	realfile = open_with_fake_path(&file->f_path, flags, realinode,
> +				       current_cred());
>  	revert_creds(old_cred);
>  
>  	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
> @@ -50,7 +51,7 @@ static int ovl_change_flags(struct file *file, unsigned int flags)
>  	int err;
>  
>  	/* No atime modificaton on underlying */
> -	flags |= O_NOATIME;
> +	flags |= O_NOATIME | FMODE_NONOTIFY;
>  
>  	/* If some flag changed that cannot be changed then something's amiss */
>  	if (WARN_ON((file->f_flags ^ flags) & ~OVL_SETFL_MASK))
> 


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