ext4 crypto: implement the ext4 decryption read path

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Ildar Muslukhov <ildarm@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

3 files changed, 88 insertions, 3 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index fcc6c1349186..b132a3c6b6fb 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -218,6 +218,13 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
 
 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 {
+        struct inode *inode = file->f_mapping->host;
+
+        if (ext4_encrypted_inode(inode)) {
+                int err = ext4_generate_encryption_key(inode);
+                if (err)
+                        return 0;
+        }
         file_accessed(file);
         if (IS_DAX(file_inode(file))) {
                 vma->vm_ops = &ext4_dax_vm_ops;
@@ -235,6 +242,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
         struct vfsmount *mnt = filp->f_path.mnt;
         struct path path;
         char buf[64], *cp;
+        int ret;
 
         if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
                      !(sb->s_flags & MS_RDONLY))) {
@@ -273,11 +281,17 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
          * writing and the journal is present
          */
         if (filp->f_mode & FMODE_WRITE) {
-                int ret = ext4_inode_attach_jinode(inode);
+                ret = ext4_inode_attach_jinode(inode);
                 if (ret < 0)
                         return ret;
         }
-        return dquot_file_open(inode, filp);
+        ret = dquot_file_open(inode, filp);
+        if (!ret && ext4_encrypted_inode(inode)) {
+                ret = ext4_generate_encryption_key(inode);
+                if (ret)
+                        ret = -EACCES;
+        }
+        return ret;
 }
 
 /*
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7c4527e10ae4..8b4fe626919a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3370,6 +3370,13 @@ static int __ext4_block_zero_page_range(handle_t *handle,
                 /* Uhhuh. Read error. Complain and punt. */
                 if (!buffer_uptodate(bh))
                         goto unlock;
+                if (S_ISREG(inode->i_mode) &&
+                    ext4_encrypted_inode(inode)) {
+                        /* We expect the key to be set. */
+                        BUG_ON(!ext4_has_encryption_key(inode));
+                        BUG_ON(blocksize != PAGE_CACHE_SIZE);
+                        WARN_ON_ONCE(ext4_decrypt_one(inode, page));
+                }
         }
         if (ext4_should_journal_data(inode)) {
                 BUFFER_TRACE(bh, "get write access");
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index fff9fe6aacf8..171b9ac4b45e 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -47,6 +47,46 @@
 #include "ext4.h"
 
 /*
+ * Call ext4_decrypt on every single page, reusing the encryption
+ * context.
+ */
+static void completion_pages(struct work_struct *work)
+{
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+        struct ext4_crypto_ctx *ctx =
+                container_of(work, struct ext4_crypto_ctx, work);
+        struct bio      *bio    = ctx->bio;
+        struct bio_vec  *bv;
+        int             i;
+
+        bio_for_each_segment_all(bv, bio, i) {
+                struct page *page = bv->bv_page;
+
+                int ret = ext4_decrypt(ctx, page);
+                if (ret) {
+                        WARN_ON_ONCE(1);
+                        SetPageError(page);
+                } else
+                        SetPageUptodate(page);
+                unlock_page(page);
+        }
+        ext4_release_crypto_ctx(ctx);
+        bio_put(bio);
+#else
+        BUG();
+#endif
+}
+
+static inline bool ext4_bio_encrypted(struct bio *bio)
+{
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+        return unlikely(bio->bi_private != NULL);
+#else
+        return false;
+#endif
+}
+
+/*
  * I/O completion handler for multipage BIOs.
  *
  * The mpage code never puts partial pages into a BIO (except for end-of-file).
@@ -63,6 +103,18 @@ static void mpage_end_io(struct bio *bio, int err)
         struct bio_vec *bv;
         int i;
 
+        if (ext4_bio_encrypted(bio)) {
+                struct ext4_crypto_ctx *ctx = bio->bi_private;
+
+                if (err) {
+                        ext4_release_crypto_ctx(ctx);
+                } else {
+                        INIT_WORK(&ctx->work, completion_pages);
+                        ctx->bio = bio;
+                        queue_work(ext4_read_workqueue, &ctx->work);
+                        return;
+                }
+        }
         bio_for_each_segment_all(bv, bio, i) {
                 struct page *page = bv->bv_page;
 
@@ -223,13 +275,25 @@ int ext4_mpage_readpages(struct address_space *mapping,
                         bio = NULL;
                 }
                 if (bio == NULL) {
+                        struct ext4_crypto_ctx *ctx = NULL;
+
+                        if (ext4_encrypted_inode(inode) &&
+                            S_ISREG(inode->i_mode)) {
+                                ctx = ext4_get_crypto_ctx(inode);
+                                if (IS_ERR(ctx))
+                                        goto set_error_page;
+                        }
                         bio = bio_alloc(GFP_KERNEL,
                                 min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
-                        if (!bio)
+                        if (!bio) {
+                                if (ctx)
+                                        ext4_release_crypto_ctx(ctx);
                                 goto set_error_page;
+                        }
                         bio->bi_bdev = bdev;
                         bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
                         bio->bi_end_io = mpage_end_io;
+                        bio->bi_private = ctx;
                 }
 
                 length = first_hole << blkbits;