Commit 10553a91 authored by Pankaj Raghav's avatar Pankaj Raghav Committed by Christian Brauner
Browse files

iomap: fix iomap_dio_zero() for fs bs > system page size 



iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
< fs block size. iomap_dio_zero() has an implicit assumption that fs block
size < page_size. This is true for most filesystems at the moment.

If the block size > page size, this will send the contents of the page
next to zero page(as len > PAGE_SIZE) to the underlying block device,
causing FS corruption.

iomap is a generic infrastructure and it should not make any assumptions
about the fs block size and the page size of the system.

Signed-off-by: default avatarPankaj Raghav <p.raghav@samsung.com>
Link: https://lore.kernel.org/r/20240822135018.1931258-7-kernel@pankajraghav.com


Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarDaniel Gomez <da.gomez@samsung.com>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 743a2753

fs/iomap/buffered-io.c

+2 −2
Original line number Diff line number Diff line
@@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc, 
}

EXPORT_SYMBOL_GPL(iomap_writepages);



static int __init iomap_init(void)

static int __init iomap_buffered_init(void)

{

	return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),

			   offsetof(struct iomap_ioend, io_bio),

			   BIOSET_NEED_BVECS);

}

fs_initcall(iomap_init);
 
fs_initcall(iomap_buffered_init);

fs/iomap/direct-io.c

+39 −6
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/iomap.h>

#include <linux/backing-dev.h>

#include <linux/uio.h>

#include <linux/set_memory.h>

#include <linux/task_io_accounting_ops.h>

#include "trace.h"
@@ -27,6 +28,13 @@ 
#define IOMAP_DIO_WRITE		(1U << 30)

#define IOMAP_DIO_DIRTY		(1U << 31)



/*

 * Used for sub block zeroing in iomap_dio_zero()

 */

#define IOMAP_ZERO_PAGE_SIZE (SZ_64K)

#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE))

static struct page *zero_page;



struct iomap_dio {

	struct kiocb		*iocb;

	const struct iomap_dio_ops *dops;
@@ -232,13 +240,20 @@ void iomap_dio_bio_end_io(struct bio *bio) 
}

EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io);



static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,

static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,

		loff_t pos, unsigned len)

{

	struct inode *inode = file_inode(dio->iocb->ki_filp);

	struct page *page = ZERO_PAGE(0);

	struct bio *bio;



	if (!len)

		return 0;

	/*

	 * Max block size supported is 64k

	 */

	if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE))

		return -EINVAL;



	bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE);

	fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits,

				  GFP_KERNEL);
@@ -246,8 +261,9 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, 
	bio->bi_private = dio;

	bio->bi_end_io = iomap_dio_bio_end_io;



	__bio_add_page(bio, page, len, 0);

	__bio_add_page(bio, zero_page, len, 0);

	iomap_dio_submit_bio(iter, dio, bio, pos);

	return 0;

}



/*
@@ -356,8 +372,10 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, 
	if (need_zeroout) {

		/* zero out from the start of the block to the write offset */

		pad = pos & (fs_block_size - 1);

		if (pad)

			iomap_dio_zero(iter, dio, pos - pad, pad);



		ret = iomap_dio_zero(iter, dio, pos - pad, pad);

		if (ret)

			goto out;

	}



	/*
@@ -431,7 +449,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, 
		/* zero out from the end of the write to the end of the block */

		pad = pos & (fs_block_size - 1);

		if (pad)

			iomap_dio_zero(iter, dio, pos, fs_block_size - pad);

			ret = iomap_dio_zero(iter, dio, pos,

					     fs_block_size - pad);

	}

out:

	/* Undo iter limitation to current extent */
@@ -753,3 +772,17 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 
	return iomap_dio_complete(dio);

}

EXPORT_SYMBOL_GPL(iomap_dio_rw);



static int __init iomap_dio_init(void)

{

	zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,

				IOMAP_ZERO_PAGE_ORDER);



	if (!zero_page)

		return -ENOMEM;



	set_memory_ro((unsigned long)page_address(zero_page),

		      1U << IOMAP_ZERO_PAGE_ORDER);

	return 0;

}

fs_initcall(iomap_dio_init);