ext4 crypto: add symlink encryption

Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 65 insertions, 20 deletions

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 4c84db862891..d201426b8d39 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3193,16 +3193,24 @@ static int ext4_symlink(struct inode *dir,
 {
         handle_t *handle;
         struct inode *inode;
-        int l, err, retries = 0;
+        int err, len = strlen(symname);
         int credits;
+        bool encryption_required;
+        struct ext4_str disk_link;
+        struct ext4_encrypted_symlink_data *sd = NULL;
 
-        l = strlen(symname)+1;
-        if (l > dir->i_sb->s_blocksize)
+        disk_link.len = len + 1;
+        disk_link.name = (char *) symname;
+
+        encryption_required = ext4_encrypted_inode(dir);
+        if (encryption_required)
+                disk_link.len = encrypted_symlink_data_len(len) + 1;
+        if (disk_link.len > dir->i_sb->s_blocksize)
                 return -ENAMETOOLONG;
 
         dquot_initialize(dir);
 
-        if (l > EXT4_N_BLOCKS * 4) {
+        if ((disk_link.len > EXT4_N_BLOCKS * 4)) {
                 /*
                  * For non-fast symlinks, we just allocate inode and put it on
                  * orphan list in the first transaction => we need bitmap,
@@ -3221,16 +3229,49 @@ static int ext4_symlink(struct inode *dir,
                 credits = EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
                           EXT4_INDEX_EXTRA_TRANS_BLOCKS + 3;
         }
-retry:
+
         inode = ext4_new_inode_start_handle(dir, S_IFLNK|S_IRWXUGO,
                                             &dentry->d_name, 0, NULL,
                                             EXT4_HT_DIR, credits);
         handle = ext4_journal_current_handle();
-        err = PTR_ERR(inode);
-        if (IS_ERR(inode))
-                goto out_stop;
+        if (IS_ERR(inode)) {
+                if (handle)
+                        ext4_journal_stop(handle);
+                return PTR_ERR(inode);
+        }
+
+        if (encryption_required) {
+                struct ext4_fname_crypto_ctx *ctx = NULL;
+                struct qstr istr;
+                struct ext4_str ostr;
+
+                sd = kzalloc(disk_link.len, GFP_NOFS);
+                if (!sd) {
+                        err = -ENOMEM;
+                        goto err_drop_inode;
+                }
+                err = ext4_inherit_context(dir, inode);
+                if (err)
+                        goto err_drop_inode;
+                ctx = ext4_get_fname_crypto_ctx(inode,
+                                                inode->i_sb->s_blocksize);
+                if (IS_ERR_OR_NULL(ctx)) {
+                        /* We just set the policy, so ctx should not be NULL */
+                        err = (ctx == NULL) ? -EIO : PTR_ERR(ctx);
+                        goto err_drop_inode;
+                }
+                istr.name = (const unsigned char *) symname;
+                istr.len = len;
+                ostr.name = sd->encrypted_path;
+                err = ext4_fname_usr_to_disk(ctx, &istr, &ostr);
+                ext4_put_fname_crypto_ctx(&ctx);
+                if (err < 0)
+                        goto err_drop_inode;
+                sd->len = cpu_to_le16(ostr.len);
+                disk_link.name = (char *) sd;
+        }
 
-        if (l > EXT4_N_BLOCKS * 4) {
+        if ((disk_link.len > EXT4_N_BLOCKS * 4)) {
                 inode->i_op = &ext4_symlink_inode_operations;
                 ext4_set_aops(inode);
                 /*
@@ -3246,9 +3287,10 @@ retry:
                 drop_nlink(inode);
                 err = ext4_orphan_add(handle, inode);
                 ext4_journal_stop(handle);
+                handle = NULL;
                 if (err)
                         goto err_drop_inode;
-                err = __page_symlink(inode, symname, l, 1);
+                err = __page_symlink(inode, disk_link.name, disk_link.len, 1);
                 if (err)
                         goto err_drop_inode;
                 /*
@@ -3260,34 +3302,37 @@ retry:
                                 EXT4_INDEX_EXTRA_TRANS_BLOCKS + 1);
                 if (IS_ERR(handle)) {
                         err = PTR_ERR(handle);
+                        handle = NULL;
                         goto err_drop_inode;
                 }
                 set_nlink(inode, 1);
                 err = ext4_orphan_del(handle, inode);
-                if (err) {
-                        ext4_journal_stop(handle);
-                        clear_nlink(inode);
+                if (err)
                         goto err_drop_inode;
-                }
         } else {
                 /* clear the extent format for fast symlink */
                 ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
-                inode->i_op = &ext4_fast_symlink_inode_operations;
-                memcpy((char *)&EXT4_I(inode)->i_data, symname, l);
-                inode->i_size = l-1;
+                inode->i_op = encryption_required ?
+                        &ext4_symlink_inode_operations :
+                        &ext4_fast_symlink_inode_operations;
+                memcpy((char *)&EXT4_I(inode)->i_data, disk_link.name,
+                       disk_link.len);
+                inode->i_size = disk_link.len - 1;
         }
         EXT4_I(inode)->i_disksize = inode->i_size;
         err = ext4_add_nondir(handle, dentry, inode);
         if (!err && IS_DIRSYNC(dir))
                 ext4_handle_sync(handle);
 
-out_stop:
         if (handle)
                 ext4_journal_stop(handle);
-        if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
-                goto retry;
+        kfree(sd);
         return err;
 err_drop_inode:
+        if (handle)
+                ext4_journal_stop(handle);
+        kfree(sd);
+        clear_nlink(inode);
         unlock_new_inode(inode);
         iput(inode);
         return err;