ext4 crypto: implement the ext4 decryption read path
Michael Halcrow [Wed, 15 Apr 2015 00:49:49 +0000 (20:49 -0400)]
Change-Id: I66c32c7fa9ad6269f3ea929d773a2b35bccb2290
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>
Signed-off-by: Theodore Ts'o <tytso@google.com>

fs/ext4/file.c
fs/ext4/inode.c
fs/ext4/readpage.c

index 5833ccf..0575ff8 100644 (file)
@@ -338,6 +338,13 @@ 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);
        vma->vm_ops = &ext4_file_vm_ops;
        return 0;
@@ -350,6 +357,7 @@ 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))) {
@@ -388,11 +396,17 @@ 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;
 }
 
 /*
index 042d091..bb7ce8c 100644 (file)
@@ -3411,6 +3411,13 @@ 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");
index ae7c569..7fc957e 100644 (file)
 #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_sector = blocks[0] << (blkbits - 9);
                        bio->bi_end_io = mpage_end_io;
+                       bio->bi_private = ctx;
                }
 
                length = first_hole << blkbits;