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iomap: move the iomap_dio_rw ->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@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2019-09-19 15:32:45 -07:00 committed by Darrick J. Wong
parent 6fe7b99014
commit 838c4f3d75
3 changed files with 22 additions and 15 deletions
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21
fs/iomap/direct-io.c
View File

@ -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;

6
fs/xfs/xfs_file.c
View File

@ -442,6 +442,10 @@ out:
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
*
@ -542,7 +546,7 @@ 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

10
include/linux/iomap.h
View File

@ -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