[v2] ovl: do not generate duplicate fsnotify events for "fake" path
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Message ID 20190424163950.14123-1-amir73il@gmail.com
State New
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  • [v2] ovl: do not generate duplicate fsnotify events for "fake" path
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Commit Message

Amir Goldstein April 24, 2019, 4:39 p.m. UTC
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@gmail.com>
Fixes: d1d04ef8572b ("ovl: stack file ops")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

Miklos,

V1 was addressed to Jan and was trying to teach fsnotify about fake path.
V2 leaves fsnotify subsystem alone and just sets the FMODE_NONOTIFY
flag on realfile. All the rest of the complications with mark mounts
are irrelevant.

Same extended fanotify06 that was used to verify V1 also verified V2.

Thanks,
Amir.

 fs/overlayfs/file.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Murphy Zhou April 28, 2019, 3:08 a.m. UTC | #1
On Thu, Apr 25, 2019 at 12:39 AM Amir Goldstein <amir73il@gmail.com> wrote:
>
> 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@gmail.com>
> Fixes: d1d04ef8572b ("ovl: stack file ops")
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>
> Miklos,
>
> V1 was addressed to Jan and was trying to teach fsnotify about fake path.
> V2 leaves fsnotify subsystem alone and just sets the FMODE_NONOTIFY
> flag on realfile. All the rest of the complications with mark mounts
> are irrelevant.
>
> Same extended fanotify06 that was used to verify V1 also verified V2.

Thanks for fixing this!

My overlayfs tests on this patch looks good.

M

>
> Thanks,
> Amir.
>
>  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 ddfd93f13cc5..7d2f01957e40 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))
> --
> 2.17.1
>
Miklos Szeredi May 6, 2019, 11:58 a.m. UTC | #2
On Sat, Apr 27, 2019 at 11:09 PM Murphy Zhou <jencce.kernel@gmail.com> wrote:
>
> On Thu, Apr 25, 2019 at 12:39 AM Amir Goldstein <amir73il@gmail.com> wrote:
> >
> > 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@gmail.com>
> > Fixes: d1d04ef8572b ("ovl: stack file ops")
> > Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> > ---
> >
> > Miklos,
> >
> > V1 was addressed to Jan and was trying to teach fsnotify about fake path.
> > V2 leaves fsnotify subsystem alone and just sets the FMODE_NONOTIFY
> > flag on realfile. All the rest of the complications with mark mounts
> > are irrelevant.
> >
> > Same extended fanotify06 that was used to verify V1 also verified V2.
>
> Thanks for fixing this!
>
> My overlayfs tests on this patch looks good.

Thanks, applied.

Miklos

Patch
diff mbox series

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index ddfd93f13cc5..7d2f01957e40 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))