On Tue, Sep 03, 2019 at 03:03:27PM +0200, Christoph Hellwig wrote:
> Add a new iomap_dio_ops structure that for now just contains the end_io
> handler. This avoid storing the function pointer in a mutable structure,
> which is a possible exploit vector for kernel code execution, and prepares
> for adding a submit_io handler that btrfs needs.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/iomap/direct-io.c | 21 ++++++++++-----------
> fs/xfs/xfs_file.c | 6 +++++-
> include/linux/iomap.h | 10 +++++++---
> 3 files changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 2ccf1c6460d4..1fc28c2da279 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -24,7 +24,7 @@
>
> struct iomap_dio {
> struct kiocb *iocb;
> - iomap_dio_end_io_t *end_io;
> + const struct iomap_dio_ops *dops;
> loff_t i_size;
> loff_t size;
> atomic_t ref;
> @@ -72,15 +72,14 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
>
> static ssize_t iomap_dio_complete(struct iomap_dio *dio)
> {
> + const struct iomap_dio_ops *dops = dio->dops;
> struct kiocb *iocb = dio->iocb;
> struct inode *inode = file_inode(iocb->ki_filp);
> loff_t offset = iocb->ki_pos;
> - ssize_t ret;
> + ssize_t ret = dio->error;
>
> - if (dio->end_io)
> - ret = dio->end_io(iocb, dio->size, dio->error, dio->flags);
> - else
> - ret = dio->error;
> + if (dops && dops->end_io)
> + ret = dops->end_io(iocb, dio->size, ret, dio->flags);
>
> if (likely(!ret)) {
> ret = dio->size;
> @@ -98,9 +97,9 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
> * one is a pretty crazy thing to do, so we don't support it 100%. If
> * this invalidation fails, tough, the write still worked...
> *
> - * And this page cache invalidation has to be after dio->end_io(), as
> - * some filesystems convert unwritten extents to real allocations in
> - * end_io() when necessary, otherwise a racing buffer read would cache
> + * And this page cache invalidation has to be after ->end_io(), as some
> + * filesystems convert unwritten extents to real allocations in
> + * ->end_io() when necessary, otherwise a racing buffer read would cache
> * zeros from unwritten extents.
> */
> if (!dio->error &&
> @@ -393,7 +392,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
> */
> ssize_t
> iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> - const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
> + const struct iomap_ops *ops, const struct iomap_dio_ops *dops)
> {
> struct address_space *mapping = iocb->ki_filp->f_mapping;
> struct inode *inode = file_inode(iocb->ki_filp);
> @@ -418,7 +417,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> atomic_set(&dio->ref, 1);
> dio->size = 0;
> dio->i_size = i_size_read(inode);
> - dio->end_io = end_io;
> + dio->dops = dops;
> dio->error = 0;
> dio->flags = 0;
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 3d8e6db9ef77..1ffb179f35d2 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -443,6 +443,10 @@ xfs_dio_write_end_io(
> return error;
> }
>
> +static const struct iomap_dio_ops xfs_dio_write_ops = {
> + .end_io = xfs_dio_write_end_io,
> +};
> +
> /*
> * xfs_file_dio_aio_write - handle direct IO writes
> *
> @@ -543,7 +547,7 @@ xfs_file_dio_aio_write(
> }
>
> trace_xfs_file_direct_write(ip, count, iocb->ki_pos);
> - ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, xfs_dio_write_end_io);
> + ret = iomap_dio_rw(iocb, from, &xfs_iomap_ops, &xfs_dio_write_ops);
>
> /*
> * If unaligned, this is the only IO in-flight. If it has not yet
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 50bb746d2216..7aa5d6117936 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -188,10 +188,14 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
> */
> #define IOMAP_DIO_UNWRITTEN (1 << 0) /* covers unwritten extent(s) */
> #define IOMAP_DIO_COW (1 << 1) /* covers COW extent(s) */
> -typedef int (iomap_dio_end_io_t)(struct kiocb *iocb, ssize_t size, int error,
> - unsigned int flags);
> +
> +struct iomap_dio_ops {
> + int (*end_io)(struct kiocb *iocb, ssize_t size, int error,
> + unsigned flags);
> +};
> +
> ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
> - const struct iomap_ops *ops, iomap_dio_end_io_t end_io);
> + const struct iomap_ops *ops, const struct iomap_dio_ops *dops);
> int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);
>
> #ifdef CONFIG_SWAP
> --
> 2.20.1
>
