ext4: add fs-verity read support
Make ext4_mpage_readpages() verify data as it is read from fs-verity
files, using the helper functions from fs/verity/.
To support both encryption and verity simultaneously, this required
refactoring the decryption workflow into a generic "post-read
processing" workflow which can do decryption, verification, or both.
The case where the ext4 block size is not equal to the PAGE_SIZE is not
supported yet, since in that case ext4_mpage_readpages() sometimes falls
back to block_read_full_page(), which does not support fs-verity yet.
Co-developed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index c916017..a30b203 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -47,13 +47,103 @@
#include "ext4.h"
-static inline bool ext4_bio_encrypted(struct bio *bio)
+#define NUM_PREALLOC_POST_READ_CTXS 128
+
+static struct kmem_cache *bio_post_read_ctx_cache;
+static mempool_t *bio_post_read_ctx_pool;
+
+/* postprocessing steps for read bios */
+enum bio_post_read_step {
+ STEP_INITIAL = 0,
+ STEP_DECRYPT,
+ STEP_VERITY,
+};
+
+struct bio_post_read_ctx {
+ struct bio *bio;
+ struct work_struct work;
+ unsigned int cur_step;
+ unsigned int enabled_steps;
+};
+
+static void __read_end_io(struct bio *bio)
{
-#ifdef CONFIG_FS_ENCRYPTION
- return unlikely(bio->bi_private != NULL);
-#else
- return false;
-#endif
+ struct page *page;
+ struct bio_vec *bv;
+ struct bvec_iter_all iter_all;
+
+ bio_for_each_segment_all(bv, bio, iter_all) {
+ page = bv->bv_page;
+
+ /* PG_error was set if any post_read step failed */
+ if (bio->bi_status || PageError(page)) {
+ ClearPageUptodate(page);
+ /* will re-read again later */
+ ClearPageError(page);
+ } else {
+ SetPageUptodate(page);
+ }
+ unlock_page(page);
+ }
+ if (bio->bi_private)
+ mempool_free(bio->bi_private, bio_post_read_ctx_pool);
+ bio_put(bio);
+}
+
+static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
+
+static void decrypt_work(struct work_struct *work)
+{
+ struct bio_post_read_ctx *ctx =
+ container_of(work, struct bio_post_read_ctx, work);
+
+ fscrypt_decrypt_bio(ctx->bio);
+
+ bio_post_read_processing(ctx);
+}
+
+static void verity_work(struct work_struct *work)
+{
+ struct bio_post_read_ctx *ctx =
+ container_of(work, struct bio_post_read_ctx, work);
+
+ fsverity_verify_bio(ctx->bio);
+
+ bio_post_read_processing(ctx);
+}
+
+static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
+{
+ /*
+ * We use different work queues for decryption and for verity because
+ * verity may require reading metadata pages that need decryption, and
+ * we shouldn't recurse to the same workqueue.
+ */
+ switch (++ctx->cur_step) {
+ case STEP_DECRYPT:
+ if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
+ INIT_WORK(&ctx->work, decrypt_work);
+ fscrypt_enqueue_decrypt_work(&ctx->work);
+ return;
+ }
+ ctx->cur_step++;
+ /* fall-through */
+ case STEP_VERITY:
+ if (ctx->enabled_steps & (1 << STEP_VERITY)) {
+ INIT_WORK(&ctx->work, verity_work);
+ fsverity_enqueue_verify_work(&ctx->work);
+ return;
+ }
+ ctx->cur_step++;
+ /* fall-through */
+ default:
+ __read_end_io(ctx->bio);
+ }
+}
+
+static bool bio_post_read_required(struct bio *bio)
+{
+ return bio->bi_private && !bio->bi_status;
}
/*
@@ -70,30 +160,53 @@ static inline bool ext4_bio_encrypted(struct bio *bio)
*/
static void mpage_end_io(struct bio *bio)
{
- struct bio_vec *bv;
- struct bvec_iter_all iter_all;
+ if (bio_post_read_required(bio)) {
+ struct bio_post_read_ctx *ctx = bio->bi_private;
- if (ext4_bio_encrypted(bio)) {
- if (bio->bi_status) {
- fscrypt_release_ctx(bio->bi_private);
- } else {
- fscrypt_enqueue_decrypt_bio(bio->bi_private, bio);
- return;
- }
+ ctx->cur_step = STEP_INITIAL;
+ bio_post_read_processing(ctx);
+ return;
}
- bio_for_each_segment_all(bv, bio, iter_all) {
- struct page *page = bv->bv_page;
+ __read_end_io(bio);
+}
- if (!bio->bi_status) {
- SetPageUptodate(page);
- } else {
- ClearPageUptodate(page);
- SetPageError(page);
- }
- unlock_page(page);
+static inline bool ext4_need_verity(const struct inode *inode, pgoff_t idx)
+{
+ return fsverity_active(inode) &&
+ idx < DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
+}
+
+static struct bio_post_read_ctx *get_bio_post_read_ctx(struct inode *inode,
+ struct bio *bio,
+ pgoff_t first_idx)
+{
+ unsigned int post_read_steps = 0;
+ struct bio_post_read_ctx *ctx = NULL;
+
+ if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
+ post_read_steps |= 1 << STEP_DECRYPT;
+
+ if (ext4_need_verity(inode, first_idx))
+ post_read_steps |= 1 << STEP_VERITY;
+
+ if (post_read_steps) {
+ ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
+ if (!ctx)
+ return ERR_PTR(-ENOMEM);
+ ctx->bio = bio;
+ ctx->enabled_steps = post_read_steps;
+ bio->bi_private = ctx;
}
+ return ctx;
+}
- bio_put(bio);
+static inline loff_t ext4_readpage_limit(struct inode *inode)
+{
+ if (IS_ENABLED(CONFIG_FS_VERITY) &&
+ (IS_VERITY(inode) || ext4_verity_in_progress(inode)))
+ return inode->i_sb->s_maxbytes;
+
+ return i_size_read(inode);
}
int ext4_mpage_readpages(struct address_space *mapping,
@@ -141,7 +254,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
last_block = block_in_file + nr_pages * blocks_per_page;
- last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
+ last_block_in_file = (ext4_readpage_limit(inode) +
+ blocksize - 1) >> blkbits;
if (last_block > last_block_in_file)
last_block = last_block_in_file;
page_block = 0;
@@ -218,6 +332,9 @@ int ext4_mpage_readpages(struct address_space *mapping,
zero_user_segment(page, first_hole << blkbits,
PAGE_SIZE);
if (first_hole == 0) {
+ if (ext4_need_verity(inode, page->index) &&
+ !fsverity_verify_page(page))
+ goto set_error_page;
SetPageUptodate(page);
unlock_page(page);
goto next_page;
@@ -241,18 +358,16 @@ int ext4_mpage_readpages(struct address_space *mapping,
bio = NULL;
}
if (bio == NULL) {
- struct fscrypt_ctx *ctx = NULL;
+ struct bio_post_read_ctx *ctx;
- if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode)) {
- ctx = fscrypt_get_ctx(GFP_NOFS);
- if (IS_ERR(ctx))
- goto set_error_page;
- }
bio = bio_alloc(GFP_KERNEL,
min_t(int, nr_pages, BIO_MAX_PAGES));
- if (!bio) {
- if (ctx)
- fscrypt_release_ctx(ctx);
+ if (!bio)
+ goto set_error_page;
+ ctx = get_bio_post_read_ctx(inode, bio, page->index);
+ if (IS_ERR(ctx)) {
+ bio_put(bio);
+ bio = NULL;
goto set_error_page;
}
bio_set_dev(bio, bdev);
@@ -293,3 +408,29 @@ int ext4_mpage_readpages(struct address_space *mapping,
submit_bio(bio);
return 0;
}
+
+int __init ext4_init_post_read_processing(void)
+{
+ bio_post_read_ctx_cache =
+ kmem_cache_create("ext4_bio_post_read_ctx",
+ sizeof(struct bio_post_read_ctx), 0, 0, NULL);
+ if (!bio_post_read_ctx_cache)
+ goto fail;
+ bio_post_read_ctx_pool =
+ mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
+ bio_post_read_ctx_cache);
+ if (!bio_post_read_ctx_pool)
+ goto fail_free_cache;
+ return 0;
+
+fail_free_cache:
+ kmem_cache_destroy(bio_post_read_ctx_cache);
+fail:
+ return -ENOMEM;
+}
+
+void ext4_exit_post_read_processing(void)
+{
+ mempool_destroy(bio_post_read_ctx_pool);
+ kmem_cache_destroy(bio_post_read_ctx_cache);
+}
