[PATCH 08/24] iomap: integrate fs-verity verification into iomap's read path

[Andrey Albershteyn <aalbersh@redhat.com>]

From: Andrey Albershteyn <aalbersh@redhat.com>

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>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: fix doc warning]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/iomap/buffered-io.c | 30 ++++++++++++++++++++++++++++--
 include/linux/iomap.h  |  5 +++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d6231f4f78d9..59c0ff6fb6b7 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>
@@ -23,6 +24,8 @@
 
 #define IOEND_BATCH_SIZE	4096
 
+#define IOMAP_POOL_SIZE		(4 * (PAGE_SIZE / SECTOR_SIZE))
+
 /*
  * Structure allocated for each folio to track per-block uptodate, dirty state
  * and I/O completions.
@@ -362,6 +365,19 @@ static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
 		 !(srcmap->flags & IOMAP_F_BEYOND_EOF));
 }
 
+#ifdef CONFIG_FS_VERITY
+void
+iomap_read_fsverity_end_io_work(struct work_struct *work)
+{
+	struct iomap_read_ioend *fbio =
+		container_of(work, struct iomap_read_ioend, io_work);
+
+	fsverity_verify_bio(&fbio->io_bio);
+	iomap_read_end_io(&fbio->io_bio);
+}
+
+#endif /* CONFIG_FS_VERITY */
+
 static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 		struct iomap_readpage_ctx *ctx, loff_t offset)
 {
@@ -376,6 +392,10 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
 	struct iomap_read_ioend *ioend;
 	const struct iomap *srcmap = iomap_iter_srcmap(iter);
 
+	/* Fail reads from broken fsverity files immediately. */
+	if (IS_VERITY(iter->inode) && !fsverity_active(iter->inode))
+		return -EIO;
+
 	if (iomap->type == IOMAP_INLINE)
 		return iomap_read_inline_data(iter, folio);
 
@@ -387,6 +407,12 @@ 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 (!(srcmap->flags & IOMAP_F_BEYOND_EOF) &&
+		    fsverity_active(iter->inode) &&
+		    !fsverity_verify_blocks(folio, plen, poff)) {
+			return -EIO;
+		}
+
 		iomap_set_range_uptodate(folio, poff, plen);
 		goto done;
 	}
@@ -2176,13 +2202,13 @@ static int __init iomap_buffered_init(void)
 	int error = 0;
 
 	error = bioset_init(&iomap_read_ioend_bioset,
-			   4 * (PAGE_SIZE / SECTOR_SIZE),
+			   IOMAP_POOL_SIZE,
 			   offsetof(struct iomap_read_ioend, io_bio),
 			   BIOSET_NEED_BVECS);
 	if (error)
 		return error;
 
-	return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE),
+	return bioset_init(&iomap_ioend_bioset, IOMAP_POOL_SIZE,
 			   offsetof(struct iomap_ioend, io_bio),
 			   BIOSET_NEED_BVECS);
 }
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 261772431fae..e4704b337ac1 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -326,6 +326,11 @@ struct iomap_readpage_ctx {
 };
 
 void iomap_read_end_io(struct bio *bio);
+#ifdef CONFIG_FS_VERITY
+void iomap_read_fsverity_end_io_work(struct work_struct *work);
+#else
+#define iomap_read_fsverity_end_io_work (0)
+#endif /* CONFIG_FS_VERITY */
 ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
 		const struct iomap_ops *ops, void *private);
 int iomap_read_folio_ctx(struct iomap_readpage_ctx *ctx,
-- 
2.47.0