On Mon 03-02-25 23:32:04, Amir Goldstein wrote:
> Most pseudo files are not applicable for fsnotify events at all,
> let alone to the new pre-content events.
>
> Disable notifications to all files allocated with alloc_file_pseudo()
> and enable legacy inotify events for the specific cases of pipe and
> socket, which have known users of inotify events.
>
> Pre-content events are also kept disabled for sockets and pipes.
>
> Fixes: 20bf82a898b6 ("mm: don't allow huge faults for files with pre content watches")
> Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-fsdevel/20250131121703.1e4d00a7.alex.williamson@xxxxxxxxxx/
> Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wi2pThSVY=zhO=ZKxViBj5QCRX-=AS2+rVknQgJnHXDFg@xxxxxxxxxxxxxx/
> Tested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/file_table.c | 11 +++++++++++
> fs/open.c | 4 ++--
> fs/pipe.c | 6 ++++++
> net/socket.c | 5 +++++
> 4 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/file_table.c b/fs/file_table.c
> index f0291a66f9db4..35b93da6c5cb1 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -375,7 +375,13 @@ struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
> if (IS_ERR(file)) {
> ihold(inode);
> path_put(&path);
> + return file;
> }
> + /*
> + * Disable all fsnotify events for pseudo files by default.
> + * They may be enabled by caller with file_set_fsnotify_mode().
> + */
> + file_set_fsnotify_mode(file, FMODE_NONOTIFY);
> return file;
> }
> EXPORT_SYMBOL(alloc_file_pseudo);
> @@ -400,6 +406,11 @@ struct file *alloc_file_pseudo_noaccount(struct inode *inode,
> return file;
> }
> file_init_path(file, &path, fops);
> + /*
> + * Disable all fsnotify events for pseudo files by default.
> + * They may be enabled by caller with file_set_fsnotify_mode().
> + */
> + file_set_fsnotify_mode(file, FMODE_NONOTIFY);
> return file;
> }
> EXPORT_SYMBOL_GPL(alloc_file_pseudo_noaccount);
> diff --git a/fs/open.c b/fs/open.c
> index 3fcbfff8aede8..1be20de9f283a 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -936,8 +936,8 @@ static int do_dentry_open(struct file *f,
>
> /*
> * Set FMODE_NONOTIFY_* bits according to existing permission watches.
> - * If FMODE_NONOTIFY was already set for an fanotify fd, this doesn't
> - * change anything.
> + * If FMODE_NONOTIFY mode was already set for an fanotify fd or for a
> + * pseudo file, this call will not change the mode.
> */
> file_set_fsnotify_mode_from_watchers(f);
> error = fsnotify_open_perm(f);
> diff --git a/fs/pipe.c b/fs/pipe.c
> index 94b59045ab44b..ce1af7592780d 100644
> --- a/fs/pipe.c
> +++ b/fs/pipe.c
> @@ -960,6 +960,12 @@ int create_pipe_files(struct file **res, int flags)
> res[1] = f;
> stream_open(inode, res[0]);
> stream_open(inode, res[1]);
> + /*
> + * Disable permission and pre-content events, but enable legacy
> + * inotify events for legacy users.
> + */
> + file_set_fsnotify_mode(res[0], FMODE_NONOTIFY_PERM);
> + file_set_fsnotify_mode(res[1], FMODE_NONOTIFY_PERM);
> return 0;
> }
>
> diff --git a/net/socket.c b/net/socket.c
> index 262a28b59c7f0..28bae5a942341 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -479,6 +479,11 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
> sock->file = file;
> file->private_data = sock;
> stream_open(SOCK_INODE(sock), file);
> + /*
> + * Disable permission and pre-content events, but enable legacy
> + * inotify events for legacy users.
> + */
> + file_set_fsnotify_mode(file, FMODE_NONOTIFY_PERM);
> return file;
> }
> EXPORT_SYMBOL(sock_alloc_file);
> --
> 2.34.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
