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ext4 crypto: add symlink encryption

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Signed-off-by: Uday Savagaonkar <savagaon@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o
2015-04-16 01:55:00 -04:00
parent 4461471107
commit f348c25232
5 changed files with 184 additions and 23 deletions
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96
fs/ext4/symlink.c
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@@ -22,7 +22,96 @@
#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);
@@ -31,8 +120,13 @@ static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
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_symlink_inode_operations = {
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,