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https://github.com/torvalds/linux
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b7236e21d5
This is a pretty massive patch which does a number of different things: 1) The per-inode encryption information is now stored in an allocated data structure, ext4_crypt_info, instead of directly in the node. This reduces the size usage of an in-memory inode when it is not using encryption. 2) We drop the ext4_fname_crypto_ctx entirely, and use the per-inode encryption structure instead. This remove an unnecessary memory allocation and free for the fname_crypto_ctx as well as allowing us to reuse the ctfm in a directory for multiple lookups and file creations. 3) We also cache the inode's policy information in the ext4_crypt_info structure so we don't have to continually read it out of the extended attributes. 4) We now keep the keyring key in the inode's encryption structure instead of releasing it after we are done using it to derive the per-inode key. This allows us to test to see if the key has been revoked; if it has, we prevent the use of the derived key and free it. 5) When an inode is released (or when the derived key is freed), we will use memset_explicit() to zero out the derived key, so it's not left hanging around in memory. This implies that when a user logs out, it is important to first revoke the key, and then unlink it, and then finally, to use "echo 3 > /proc/sys/vm/drop_caches" to release any decrypted pages and dcache entries from the system caches. 6) All this, and we also shrink the number of lines of code by around 100. :-) Signed-off-by: Theodore Ts'o <tytso@mit.edu>
142 lines
3.3 KiB
C
142 lines
3.3 KiB
C
/*
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* linux/fs/ext4/symlink.c
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*
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* Only fast symlinks left here - the rest is done by generic code. AV, 1999
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*
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* Copyright (C) 1992, 1993, 1994, 1995
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* Remy Card (card@masi.ibp.fr)
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* Laboratoire MASI - Institut Blaise Pascal
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* Universite Pierre et Marie Curie (Paris VI)
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*
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* from
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*
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* linux/fs/minix/symlink.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* ext4 symlink handling code
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*/
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#include <linux/fs.h>
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#include <linux/namei.h>
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#include "ext4.h"
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#include "xattr.h"
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#ifdef CONFIG_EXT4_FS_ENCRYPTION
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static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
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{
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struct page *cpage = NULL;
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char *caddr, *paddr = NULL;
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struct ext4_str cstr, pstr;
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struct inode *inode = d_inode(dentry);
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struct ext4_encrypted_symlink_data *sd;
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loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
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int res;
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u32 plen, max_size = inode->i_sb->s_blocksize;
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if (!ext4_encrypted_inode(inode))
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return page_follow_link_light(dentry, nd);
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res = ext4_setup_fname_crypto(inode);
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if (res)
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return ERR_PTR(res);
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if (ext4_inode_is_fast_symlink(inode)) {
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caddr = (char *) EXT4_I(inode)->i_data;
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max_size = sizeof(EXT4_I(inode)->i_data);
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} else {
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cpage = read_mapping_page(inode->i_mapping, 0, NULL);
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if (IS_ERR(cpage))
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return cpage;
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caddr = kmap(cpage);
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caddr[size] = 0;
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}
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/* Symlink is encrypted */
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sd = (struct ext4_encrypted_symlink_data *)caddr;
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cstr.name = sd->encrypted_path;
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cstr.len = le32_to_cpu(sd->len);
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if ((cstr.len +
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sizeof(struct ext4_encrypted_symlink_data) - 1) >
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max_size) {
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/* Symlink data on the disk is corrupted */
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res = -EIO;
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goto errout;
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}
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plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ?
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EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len;
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paddr = kmalloc(plen + 1, GFP_NOFS);
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if (!paddr) {
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res = -ENOMEM;
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goto errout;
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}
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pstr.name = paddr;
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pstr.len = plen;
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res = _ext4_fname_disk_to_usr(inode, NULL, &cstr, &pstr);
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if (res < 0)
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goto errout;
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/* Null-terminate the name */
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if (res <= plen)
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paddr[res] = '\0';
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nd_set_link(nd, paddr);
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if (cpage) {
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kunmap(cpage);
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page_cache_release(cpage);
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}
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return NULL;
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errout:
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if (cpage) {
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kunmap(cpage);
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page_cache_release(cpage);
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}
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kfree(paddr);
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return ERR_PTR(res);
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}
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static void ext4_put_link(struct dentry *dentry, struct nameidata *nd,
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void *cookie)
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{
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struct page *page = cookie;
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if (!page) {
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kfree(nd_get_link(nd));
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} else {
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kunmap(page);
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page_cache_release(page);
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}
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}
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#endif
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static void *ext4_follow_fast_link(struct dentry *dentry, struct nameidata *nd)
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{
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struct ext4_inode_info *ei = EXT4_I(d_inode(dentry));
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nd_set_link(nd, (char *) ei->i_data);
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return NULL;
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}
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const struct inode_operations ext4_symlink_inode_operations = {
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.readlink = generic_readlink,
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#ifdef CONFIG_EXT4_FS_ENCRYPTION
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.follow_link = ext4_follow_link,
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.put_link = ext4_put_link,
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#else
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.follow_link = page_follow_link_light,
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.put_link = page_put_link,
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#endif
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.setattr = ext4_setattr,
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.setxattr = generic_setxattr,
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.getxattr = generic_getxattr,
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.listxattr = ext4_listxattr,
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.removexattr = generic_removexattr,
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};
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const struct inode_operations ext4_fast_symlink_inode_operations = {
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.readlink = generic_readlink,
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.follow_link = ext4_follow_fast_link,
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.setattr = ext4_setattr,
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.setxattr = generic_setxattr,
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.getxattr = generic_getxattr,
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.listxattr = ext4_listxattr,
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.removexattr = generic_removexattr,
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};
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