On Tue, Oct 19, 2021 at 3:03 AM Gabriel Krisman Bertazi
<krisman@xxxxxxxxxxxxx> wrote:
>
> struct fanotify_error_event, at least, is preallocated and isn't able to
> to handle arbitrarily large file handles. Future-proof the code by
> complaining loudly if a handle larger than MAX_HANDLE_SZ is ever found.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/notify/fanotify/fanotify.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index cedcb1546804..45df610debbe 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -360,13 +360,23 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
> static int fanotify_encode_fh_len(struct inode *inode)
> {
> int dwords = 0;
> + int fh_len;
>
> if (!inode)
> return 0;
>
> exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
> + fh_len = dwords << 2;
>
> - return dwords << 2;
> + /*
> + * struct fanotify_error_event might be preallocated and is
> + * limited to MAX_HANDLE_SZ. This should never happen, but
> + * safeguard by forcing an invalid file handle.
> + */
> + if (WARN_ON_ONCE(fh_len > MAX_HANDLE_SZ))
> + return 0;
> +
> + return fh_len;
> }
>
> /*
> --
> 2.33.0
>
