[PATCH v5 10/24] iomap: integrate fs-verity verification into iomap's read path

Andrey Albershteyn
2024-03-04T19:12:24Z

This patch adds fs-verity verification into iomap's read path. After
BIO's io operation is complete the data are verified against
fs-verity's Merkle tree. Verification work is done in a separate
workqueue.

The read path ioend iomap_read_ioend are stored side by side with
BIOs if FS_VERITY is enabled.

Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/iomap/buffered-io.c | 92 +++++++++++++++++++++++++++++++++++++-----
1 file changed, 83 insertions(+), 9 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 093c4515b22a..e27a8af4b351 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -6,6 +6,7 @@
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/fs.h>
+#include <linux/fsverity.h>
#include <linux/iomap.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
@@ -330,6 +331,56 @@ static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
pos >= i_size_read(iter->inode);
}

+#ifdef CONFIG_FS_VERITY
+struct iomap_fsverity_bio {
+ struct work_struct work;
+ struct bio bio;
+};
+static struct bio_set iomap_fsverity_bioset;
+
+static void
+iomap_read_fsverify_end_io_work(struct work_struct *work)
+{
+ struct iomap_fsverity_bio *fbio =
+ container_of(work, struct iomap_fsverity_bio, work);
+
+ fsverity_verify_bio(&fbio->bio);
+ iomap_read_end_io(&fbio->bio);
+}
+
+static void
+iomap_read_fsverity_end_io(struct bio *bio)
+{
+ struct iomap_fsverity_bio *fbio =
+ container_of(bio, struct iomap_fsverity_bio, bio);
+
+ INIT_WORK(&fbio->work, iomap_read_fsverify_end_io_work);
+ queue_work(bio->bi_private, &fbio->work);
+}
+#endif /* CONFIG_FS_VERITY */
+
+static struct bio *iomap_read_bio_alloc(struct inode *inode,
+ struct block_device *bdev, int nr_vecs, gfp_t gfp)
+{
+ struct bio *bio;
+
+#ifdef CONFIG_FS_VERITY
+ if (fsverity_active(inode)) {
+ bio = bio_alloc_bioset(bdev, nr_vecs, REQ_OP_READ, gfp,
+ &iomap_fsverity_bioset);
+ if (bio) {
+ bio->bi_private = inode->i_sb->s_read_done_wq;
+ bio->bi_end_io = iomap_read_fsverity_end_io;
+ }
+ return bio;
+ }
+#endif
+ bio = bio_alloc(bdev, nr_vecs, REQ_OP_READ, gfp);
+ if (bio)
+ bio->bi_end_io = iomap_read_end_io;
+ return bio;
+}
+
static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
struct iomap_readpage_ctx *ctx, loff_t offset)
{
@@ -353,6 +404,12 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,

if (iomap_block_needs_zeroing(iter, pos)) {
folio_zero_range(folio, poff, plen);
+ if (fsverity_active(iter->inode) &&
+ !fsverity_verify_blocks(folio, plen, poff)) {
+ folio_set_error(folio);
+ goto done;
+ }
+
iomap_set_range_uptodate(folio, poff, plen);
goto done;
}
@@ -370,28 +427,29 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
!bio_add_folio(ctx->bio, folio, plen, poff)) {
gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
gfp_t orig_gfp = gfp;
- unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);

if (ctx->bio)
submit_bio(ctx->bio);

if (ctx->rac) /* same as readahead_gfp_mask */
gfp |= __GFP_NORETRY | __GFP_NOWARN;
- ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
- REQ_OP_READ, gfp);
+
+ ctx->bio = iomap_read_bio_alloc(iter->inode, iomap->bdev,
+ bio_max_segs(DIV_ROUND_UP(length, PAGE_SIZE)),
+ gfp);
+
/*
* If the bio_alloc fails, try it again for a single page to
* avoid having to deal with partial page reads. This emulates
* what do_mpage_read_folio does.
*/
if (!ctx->bio) {
- ctx->bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ,
- orig_gfp);
+ ctx->bio = iomap_read_bio_alloc(iter->inode,
+ iomap->bdev, 1, orig_gfp);
}
if (ctx->rac)
ctx->bio->bi_opf |= REQ_RAHEAD;
ctx->bio->bi_iter.bi_sector = sector;
- ctx->bio->bi_end_io = iomap_read_end_io;
bio_add_folio_nofail(ctx->bio, folio, plen, poff);
}

@@ -471,6 +529,7 @@ static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
* iomap_readahead - Attempt to read pages from a file.
* @rac: Describes the pages to be read.
* @ops: The operations vector for the filesystem.
+ * @wq: Workqueue for post-I/O processing (only need for fsverity)
*
* This function is for filesystems to call to implement their readahead
* address_space operation.
@@ -1996,10 +2055,25 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc,
}
EXPORT_SYMBOL_GPL(iomap_writepages);

+#define IOMAP_POOL_SIZE (4 * (PAGE_SIZE / SECTOR_SIZE))
+
static int __init iomap_init(void)
{
- return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
- offsetof(struct iomap_ioend, io_inline_bio),
- BIOSET_NEED_BVECS);
+ int error;
+
+ error = bioset_init(&iomap_ioend_bioset, IOMAP_POOL_SIZE,
+ offsetof(struct iomap_ioend, io_inline_bio),
+ BIOSET_NEED_BVECS);
+#ifdef CONFIG_FS_VERITY
+ if (error)
+ return error;
+
+ error = bioset_init(&iomap_fsverity_bioset, IOMAP_POOL_SIZE,
+ offsetof(struct iomap_fsverity_bio, bio),
+ BIOSET_NEED_BVECS);
+ if (error)
+ bioset_exit(&iomap_ioend_bioset);
+#endif
+ return error;
}
fs_initcall(iomap_init);
--
2.42.0