On Mon, Oct 25, 2021 at 10:29 PM Gabriel Krisman Bertazi
<krisman@xxxxxxxxxxxxx> wrote:
>
> FAN_FS_ERROR allows events without inodes - i.e. for file system-wide
> errors. Even though fsnotify_handle_inode_event is not currently used
> by fanotify, this patch protects other backends from cases where neither
> inode or dir are provided. Also document the constraints of the
> interface (inode and dir cannot be both NULL).
>
> Suggested-by: Amir Goldstein <amir73il@xxxxxxxxx>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> Changes since v8:
> - Convert verifications to WARN_ON
> - Require either inode or dir
> - Protect nfsd backend from !inode.
> ---
> fs/nfsd/filecache.c | 3 +++
> fs/notify/fsnotify.c | 3 +++
> include/linux/fsnotify_backend.h | 1 +
> 3 files changed, 7 insertions(+)
>
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index be3c1aad50ea..fdf89fcf1a0c 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -602,6 +602,9 @@ nfsd_file_fsnotify_handle_event(struct fsnotify_mark *mark, u32 mask,
> struct inode *inode, struct inode *dir,
> const struct qstr *name, u32 cookie)
> {
> + if (WARN_ON_ONCE(!inode))
> + return 0;
> +
> trace_nfsd_file_fsnotify_handle_event(inode, mask);
>
> /* Should be no marks on non-regular files */
> diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
> index fde3a1115a17..4034ca566f95 100644
> --- a/fs/notify/fsnotify.c
> +++ b/fs/notify/fsnotify.c
> @@ -252,6 +252,9 @@ static int fsnotify_handle_inode_event(struct fsnotify_group *group,
> if (WARN_ON_ONCE(!ops->handle_inode_event))
> return 0;
>
> + if (WARN_ON_ONCE(!inode && !dir))
> + return 0;
> +
> if ((inode_mark->mask & FS_EXCL_UNLINK) &&
> path && d_unlinked(path->dentry))
> return 0;
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 035438fe4a43..b71dc788018e 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -136,6 +136,7 @@ struct mem_cgroup;
> * @dir: optional directory associated with event -
> * if @file_name is not NULL, this is the directory that
> * @file_name is relative to.
> + * Either @inode or @dir must be non-NULL.
> * @file_name: optional file name associated with event
> * @cookie: inotify rename cookie
> *
> --
> 2.33.0
>
