On Sun, Sep 01, 2019 at 03:08:33PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> This helps filesystems to perform tasks on the bio while
> submitting for I/O. Since btrfs requires the position
> we are working on, pass pos to iomap_dio_submit_bio()
Please avoid passing function pointers in mutable data structures.
I think the best idea here is to move the end_io handler into
a structure that can be marked const, and to which we can add the
submit handler later. Something like this:
---
>From d17419b6b4124e95088858d3dcea486db6be9ffa Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Mon, 2 Sep 2019 18:39:34 +0200
Subject: iomap: move the direct I/O ->end_io callback into a structure
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>
---
fs/iomap/direct-io.c | 17 +++++++++--------
fs/xfs/xfs_file.c | 6 +++++-
include/linux/iomap.h | 9 ++++++---
3 files changed, 20 insertions(+), 12 deletions(-)
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 10517cea9682..cfe5f6a88945 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;
@@ -72,13 +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;
- if (dio->end_io) {
- ret = dio->end_io(iocb,
+ if (dops && dops->end_io) {
+ ret = dops->end_io(iocb,
dio->error ? dio->error : dio->size,
dio->flags);
} else {
@@ -101,9 +102,9 @@ 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 &&
@@ -396,7 +397,7 @@ 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);
@@ -421,7 +422,7 @@ 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 28101bbc0b78..0a2dc6b71c3c 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -440,6 +440,10 @@ 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
*
@@ -540,7 +544,7 @@ 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 bc499ceae392..d8c0769bb360 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -188,10 +188,13 @@ 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 ret,
- unsigned flags);
+
+struct iomap_dio_ops {
+ int (*end_io)(struct kiocb *iocb, ssize_t ret, 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
