Re: [PATCH 04/36] aio: sanitize ki_list handling

Darrick J. Wong
2018-03-20T00:21:14Z

On Mon, Mar 05, 2018 at 01:27:11PM -0800, Christoph Hellwig wrote:
> Instead of handcoded non-null checks always initialize ki_list to an
> empty list and use list_empty / list_empty_careful on it. While we're
> at it also error out on a double call to kiocb_set_cancel_fn instead
> of ignoring it.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Jeff Moyer <jmoyer@redhat.com>

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
> fs/aio.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 6295fc00f104..c32c315f05b5 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -555,13 +555,12 @@ void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
> struct kioctx *ctx = req->ki_ctx;
> unsigned long flags;
>
> - spin_lock_irqsave(&ctx->ctx_lock, flags);
> -
> - if (!req->ki_list.next)
> - list_add(&req->ki_list, &ctx->active_reqs);
> + if (WARN_ON_ONCE(!list_empty(&req->ki_list)))
> + return;
>
> + spin_lock_irqsave(&ctx->ctx_lock, flags);
> + list_add_tail(&req->ki_list, &ctx->active_reqs);
> req->ki_cancel = cancel;
> -
> spin_unlock_irqrestore(&ctx->ctx_lock, flags);
> }
> EXPORT_SYMBOL(kiocb_set_cancel_fn);
> @@ -1034,7 +1033,7 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
> goto out_put;
>
> percpu_ref_get(&ctx->reqs);
> -
> + INIT_LIST_HEAD(&req->ki_list);
> req->ki_ctx = ctx;
> return req;
> out_put:
> @@ -1080,7 +1079,7 @@ static void aio_complete(struct aio_kiocb *iocb, long res, long res2)
> unsigned tail, pos, head;
> unsigned long flags;
>
> - if (iocb->ki_list.next) {
> + if (!list_empty_careful(iocb->ki_list.next)) {
> unsigned long flags;
>
> spin_lock_irqsave(&ctx->ctx_lock, flags);
> --
> 2.14.2
>