ext4 crypto: add symlink encryption
Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
index 489b343..136ca0e 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -22,8 +22,97 @@
#include "ext4.h"
#include "xattr.h"
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
{
+ struct page *cpage = NULL;
+ char *caddr, *paddr = NULL;
+ struct ext4_str cstr, pstr;
+ struct inode *inode = dentry->d_inode;
+ struct ext4_fname_crypto_ctx *ctx = NULL;
+ struct ext4_encrypted_symlink_data *sd;
+ loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
+ int res;
+ u32 plen, max_size = inode->i_sb->s_blocksize;
+
+ if (!ext4_encrypted_inode(inode))
+ return page_follow_link_light(dentry, nd);
+
+ ctx = ext4_get_fname_crypto_ctx(inode, inode->i_sb->s_blocksize);
+ if (IS_ERR(ctx))
+ return ctx;
+
+ if (ext4_inode_is_fast_symlink(inode)) {
+ caddr = (char *) EXT4_I(dentry->d_inode)->i_data;
+ max_size = sizeof(EXT4_I(dentry->d_inode)->i_data);
+ } else {
+ cpage = read_mapping_page(inode->i_mapping, 0, NULL);
+ if (IS_ERR(cpage)) {
+ ext4_put_fname_crypto_ctx(&ctx);
+ return cpage;
+ }
+ caddr = kmap(cpage);
+ caddr[size] = 0;
+ }
+
+ /* Symlink is encrypted */
+ sd = (struct ext4_encrypted_symlink_data *)caddr;
+ cstr.name = sd->encrypted_path;
+ cstr.len = le32_to_cpu(sd->len);
+ if ((cstr.len +
+ sizeof(struct ext4_encrypted_symlink_data) - 1) >
+ max_size) {
+ /* Symlink data on the disk is corrupted */
+ res = -EIO;
+ goto errout;
+ }
+ plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ?
+ EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len;
+ paddr = kmalloc(plen + 1, GFP_NOFS);
+ if (!paddr) {
+ res = -ENOMEM;
+ goto errout;
+ }
+ pstr.name = paddr;
+ res = _ext4_fname_disk_to_usr(ctx, &cstr, &pstr);
+ if (res < 0)
+ goto errout;
+ /* Null-terminate the name */
+ if (res <= plen)
+ paddr[res] = '\0';
+ nd_set_link(nd, paddr);
+ ext4_put_fname_crypto_ctx(&ctx);
+ if (cpage) {
+ kunmap(cpage);
+ page_cache_release(cpage);
+ }
+ return NULL;
+errout:
+ ext4_put_fname_crypto_ctx(&ctx);
+ if (cpage) {
+ kunmap(cpage);
+ page_cache_release(cpage);
+ }
+ kfree(paddr);
+ return ERR_PTR(res);
+}
+
+static void ext4_put_link(struct dentry *dentry, struct nameidata *nd,
+ void *cookie)
+{
+ struct page *page = cookie;
+
+ if (!page) {
+ kfree(nd_get_link(nd));
+ } else {
+ kunmap(page);
+ page_cache_release(page);
+ }
+}
+#endif
+
+static void *ext4_follow_fast_link(struct dentry *dentry, struct nameidata *nd)
+{
struct ext4_inode_info *ei = EXT4_I(dentry->d_inode);
nd_set_link(nd, (char *) ei->i_data);
return NULL;
@@ -31,8 +120,13 @@
const struct inode_operations ext4_symlink_inode_operations = {
.readlink = generic_readlink,
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
+ .follow_link = ext4_follow_link,
+ .put_link = ext4_put_link,
+#else
.follow_link = page_follow_link_light,
.put_link = page_put_link,
+#endif
.setattr = ext4_setattr,
.setxattr = generic_setxattr,
.getxattr = generic_getxattr,
@@ -42,7 +136,7 @@
const struct inode_operations ext4_fast_symlink_inode_operations = {
.readlink = generic_readlink,
- .follow_link = ext4_follow_link,
+ .follow_link = ext4_follow_fast_link,
.setattr = ext4_setattr,
.setxattr = generic_setxattr,
.getxattr = generic_getxattr,