forked from Minki/linux
e37a784d8b
->i_crypt_info starts out NULL and may later be locklessly set to a non-NULL value by the cmpxchg() in fscrypt_get_encryption_info(). But ->i_crypt_info is used directly, which technically is incorrect. It's a data race, and it doesn't include the data dependency barrier needed to safely dereference the pointer on at least one architecture. Fix this by using READ_ONCE() instead. Note: we don't need to use smp_load_acquire(), since dereferencing the pointer only requires a data dependency barrier, which is already included in READ_ONCE(). We also don't need READ_ONCE() in places where ->i_crypt_info is unconditionally dereferenced, since it must have already been checked. Also downgrade the cmpxchg() to cmpxchg_release(), since RELEASE semantics are sufficient on the write side. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
498 lines
14 KiB
C
498 lines
14 KiB
C
/*
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* This contains encryption functions for per-file encryption.
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*
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* Copyright (C) 2015, Google, Inc.
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* Copyright (C) 2015, Motorola Mobility
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*
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* Written by Michael Halcrow, 2014.
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*
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* Filename encryption additions
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* Uday Savagaonkar, 2014
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* Encryption policy handling additions
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* Ildar Muslukhov, 2014
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* Add fscrypt_pullback_bio_page()
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* Jaegeuk Kim, 2015.
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*
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* This has not yet undergone a rigorous security audit.
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*
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* The usage of AES-XTS should conform to recommendations in NIST
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* Special Publication 800-38E and IEEE P1619/D16.
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*/
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#include <linux/pagemap.h>
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#include <linux/mempool.h>
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#include <linux/module.h>
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#include <linux/scatterlist.h>
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#include <linux/ratelimit.h>
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#include <linux/dcache.h>
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#include <linux/namei.h>
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#include <crypto/aes.h>
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#include <crypto/skcipher.h>
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#include "fscrypt_private.h"
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static unsigned int num_prealloc_crypto_pages = 32;
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static unsigned int num_prealloc_crypto_ctxs = 128;
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module_param(num_prealloc_crypto_pages, uint, 0444);
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MODULE_PARM_DESC(num_prealloc_crypto_pages,
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"Number of crypto pages to preallocate");
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module_param(num_prealloc_crypto_ctxs, uint, 0444);
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MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
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"Number of crypto contexts to preallocate");
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static mempool_t *fscrypt_bounce_page_pool = NULL;
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static LIST_HEAD(fscrypt_free_ctxs);
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static DEFINE_SPINLOCK(fscrypt_ctx_lock);
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static struct workqueue_struct *fscrypt_read_workqueue;
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static DEFINE_MUTEX(fscrypt_init_mutex);
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static struct kmem_cache *fscrypt_ctx_cachep;
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struct kmem_cache *fscrypt_info_cachep;
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void fscrypt_enqueue_decrypt_work(struct work_struct *work)
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{
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queue_work(fscrypt_read_workqueue, work);
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}
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EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
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/**
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* fscrypt_release_ctx() - Releases an encryption context
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* @ctx: The encryption context to release.
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*
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* If the encryption context was allocated from the pre-allocated pool, returns
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* it to that pool. Else, frees it.
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*
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* If there's a bounce page in the context, this frees that.
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*/
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void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
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{
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unsigned long flags;
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if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
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mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
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ctx->w.bounce_page = NULL;
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}
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ctx->w.control_page = NULL;
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if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
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kmem_cache_free(fscrypt_ctx_cachep, ctx);
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} else {
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spin_lock_irqsave(&fscrypt_ctx_lock, flags);
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list_add(&ctx->free_list, &fscrypt_free_ctxs);
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spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
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}
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}
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EXPORT_SYMBOL(fscrypt_release_ctx);
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/**
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* fscrypt_get_ctx() - Gets an encryption context
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* @gfp_flags: The gfp flag for memory allocation
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*
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* Allocates and initializes an encryption context.
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*
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* Return: A new encryption context on success; an ERR_PTR() otherwise.
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*/
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struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
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{
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struct fscrypt_ctx *ctx;
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unsigned long flags;
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/*
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* We first try getting the ctx from a free list because in
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* the common case the ctx will have an allocated and
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* initialized crypto tfm, so it's probably a worthwhile
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* optimization. For the bounce page, we first try getting it
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* from the kernel allocator because that's just about as fast
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* as getting it from a list and because a cache of free pages
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* should generally be a "last resort" option for a filesystem
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* to be able to do its job.
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*/
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spin_lock_irqsave(&fscrypt_ctx_lock, flags);
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ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
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struct fscrypt_ctx, free_list);
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if (ctx)
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list_del(&ctx->free_list);
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spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
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if (!ctx) {
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ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
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if (!ctx)
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return ERR_PTR(-ENOMEM);
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ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
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} else {
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ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
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}
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ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
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return ctx;
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}
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EXPORT_SYMBOL(fscrypt_get_ctx);
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void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
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const struct fscrypt_info *ci)
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{
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memset(iv, 0, ci->ci_mode->ivsize);
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iv->lblk_num = cpu_to_le64(lblk_num);
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if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
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memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
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if (ci->ci_essiv_tfm != NULL)
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crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
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}
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int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
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u64 lblk_num, struct page *src_page,
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struct page *dest_page, unsigned int len,
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unsigned int offs, gfp_t gfp_flags)
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{
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union fscrypt_iv iv;
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struct skcipher_request *req = NULL;
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DECLARE_CRYPTO_WAIT(wait);
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struct scatterlist dst, src;
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struct fscrypt_info *ci = inode->i_crypt_info;
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struct crypto_skcipher *tfm = ci->ci_ctfm;
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int res = 0;
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BUG_ON(len == 0);
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fscrypt_generate_iv(&iv, lblk_num, ci);
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req = skcipher_request_alloc(tfm, gfp_flags);
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if (!req)
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return -ENOMEM;
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skcipher_request_set_callback(
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req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
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crypto_req_done, &wait);
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sg_init_table(&dst, 1);
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sg_set_page(&dst, dest_page, len, offs);
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sg_init_table(&src, 1);
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sg_set_page(&src, src_page, len, offs);
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skcipher_request_set_crypt(req, &src, &dst, len, &iv);
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if (rw == FS_DECRYPT)
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res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
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else
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res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
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skcipher_request_free(req);
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if (res) {
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fscrypt_err(inode->i_sb,
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"%scryption failed for inode %lu, block %llu: %d",
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(rw == FS_DECRYPT ? "de" : "en"),
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inode->i_ino, lblk_num, res);
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return res;
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}
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return 0;
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}
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struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
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gfp_t gfp_flags)
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{
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ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
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if (ctx->w.bounce_page == NULL)
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return ERR_PTR(-ENOMEM);
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ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
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return ctx->w.bounce_page;
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}
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/**
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* fscypt_encrypt_page() - Encrypts a page
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* @inode: The inode for which the encryption should take place
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* @page: The page to encrypt. Must be locked for bounce-page
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* encryption.
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* @len: Length of data to encrypt in @page and encrypted
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* data in returned page.
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* @offs: Offset of data within @page and returned
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* page holding encrypted data.
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* @lblk_num: Logical block number. This must be unique for multiple
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* calls with same inode, except when overwriting
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* previously written data.
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* @gfp_flags: The gfp flag for memory allocation
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*
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* Encrypts @page using the ctx encryption context. Performs encryption
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* either in-place or into a newly allocated bounce page.
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* Called on the page write path.
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*
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* Bounce page allocation is the default.
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* In this case, the contents of @page are encrypted and stored in an
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* allocated bounce page. @page has to be locked and the caller must call
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* fscrypt_restore_control_page() on the returned ciphertext page to
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* release the bounce buffer and the encryption context.
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*
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* In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
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* fscrypt_operations. Here, the input-page is returned with its content
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* encrypted.
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*
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* Return: A page with the encrypted content on success. Else, an
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* error value or NULL.
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*/
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struct page *fscrypt_encrypt_page(const struct inode *inode,
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struct page *page,
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unsigned int len,
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unsigned int offs,
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u64 lblk_num, gfp_t gfp_flags)
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{
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struct fscrypt_ctx *ctx;
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struct page *ciphertext_page = page;
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int err;
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BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
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if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
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/* with inplace-encryption we just encrypt the page */
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err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page,
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ciphertext_page, len, offs,
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gfp_flags);
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if (err)
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return ERR_PTR(err);
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return ciphertext_page;
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}
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BUG_ON(!PageLocked(page));
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ctx = fscrypt_get_ctx(gfp_flags);
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if (IS_ERR(ctx))
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return ERR_CAST(ctx);
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/* The encryption operation will require a bounce page. */
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ciphertext_page = fscrypt_alloc_bounce_page(ctx, gfp_flags);
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if (IS_ERR(ciphertext_page))
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goto errout;
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ctx->w.control_page = page;
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err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
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page, ciphertext_page, len, offs,
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gfp_flags);
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if (err) {
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ciphertext_page = ERR_PTR(err);
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goto errout;
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}
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SetPagePrivate(ciphertext_page);
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set_page_private(ciphertext_page, (unsigned long)ctx);
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lock_page(ciphertext_page);
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return ciphertext_page;
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errout:
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fscrypt_release_ctx(ctx);
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return ciphertext_page;
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}
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EXPORT_SYMBOL(fscrypt_encrypt_page);
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/**
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* fscrypt_decrypt_page() - Decrypts a page in-place
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* @inode: The corresponding inode for the page to decrypt.
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* @page: The page to decrypt. Must be locked in case
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* it is a writeback page (FS_CFLG_OWN_PAGES unset).
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* @len: Number of bytes in @page to be decrypted.
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* @offs: Start of data in @page.
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* @lblk_num: Logical block number.
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*
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* Decrypts page in-place using the ctx encryption context.
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*
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* Called from the read completion callback.
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*
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* Return: Zero on success, non-zero otherwise.
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*/
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int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
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unsigned int len, unsigned int offs, u64 lblk_num)
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{
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if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
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BUG_ON(!PageLocked(page));
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return fscrypt_do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page,
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len, offs, GFP_NOFS);
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}
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EXPORT_SYMBOL(fscrypt_decrypt_page);
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/*
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* Validate dentries for encrypted directories to make sure we aren't
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* potentially caching stale data after a key has been added or
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* removed.
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*/
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static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct dentry *dir;
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int dir_has_key, cached_with_key;
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if (flags & LOOKUP_RCU)
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return -ECHILD;
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dir = dget_parent(dentry);
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if (!IS_ENCRYPTED(d_inode(dir))) {
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dput(dir);
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return 0;
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}
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spin_lock(&dentry->d_lock);
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cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
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spin_unlock(&dentry->d_lock);
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dir_has_key = fscrypt_has_encryption_key(d_inode(dir));
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dput(dir);
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/*
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* If the dentry was cached without the key, and it is a
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* negative dentry, it might be a valid name. We can't check
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* if the key has since been made available due to locking
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* reasons, so we fail the validation so ext4_lookup() can do
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* this check.
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*
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* We also fail the validation if the dentry was created with
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* the key present, but we no longer have the key, or vice versa.
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*/
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if ((!cached_with_key && d_is_negative(dentry)) ||
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(!cached_with_key && dir_has_key) ||
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(cached_with_key && !dir_has_key))
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return 0;
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return 1;
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}
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const struct dentry_operations fscrypt_d_ops = {
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.d_revalidate = fscrypt_d_revalidate,
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};
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void fscrypt_restore_control_page(struct page *page)
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{
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struct fscrypt_ctx *ctx;
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ctx = (struct fscrypt_ctx *)page_private(page);
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set_page_private(page, (unsigned long)NULL);
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ClearPagePrivate(page);
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unlock_page(page);
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fscrypt_release_ctx(ctx);
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}
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EXPORT_SYMBOL(fscrypt_restore_control_page);
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static void fscrypt_destroy(void)
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{
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struct fscrypt_ctx *pos, *n;
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list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
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kmem_cache_free(fscrypt_ctx_cachep, pos);
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INIT_LIST_HEAD(&fscrypt_free_ctxs);
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mempool_destroy(fscrypt_bounce_page_pool);
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fscrypt_bounce_page_pool = NULL;
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}
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/**
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* fscrypt_initialize() - allocate major buffers for fs encryption.
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* @cop_flags: fscrypt operations flags
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*
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* We only call this when we start accessing encrypted files, since it
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* results in memory getting allocated that wouldn't otherwise be used.
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*
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* Return: Zero on success, non-zero otherwise.
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*/
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int fscrypt_initialize(unsigned int cop_flags)
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{
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int i, res = -ENOMEM;
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/* No need to allocate a bounce page pool if this FS won't use it. */
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if (cop_flags & FS_CFLG_OWN_PAGES)
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return 0;
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mutex_lock(&fscrypt_init_mutex);
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if (fscrypt_bounce_page_pool)
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goto already_initialized;
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for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
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struct fscrypt_ctx *ctx;
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ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
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if (!ctx)
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goto fail;
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list_add(&ctx->free_list, &fscrypt_free_ctxs);
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}
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fscrypt_bounce_page_pool =
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mempool_create_page_pool(num_prealloc_crypto_pages, 0);
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if (!fscrypt_bounce_page_pool)
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goto fail;
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already_initialized:
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mutex_unlock(&fscrypt_init_mutex);
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return 0;
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fail:
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fscrypt_destroy();
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mutex_unlock(&fscrypt_init_mutex);
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return res;
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}
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void fscrypt_msg(struct super_block *sb, const char *level,
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const char *fmt, ...)
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{
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static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
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DEFAULT_RATELIMIT_BURST);
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struct va_format vaf;
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va_list args;
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if (!__ratelimit(&rs))
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return;
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va_start(args, fmt);
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vaf.fmt = fmt;
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vaf.va = &args;
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if (sb)
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printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf);
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else
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printk("%sfscrypt: %pV\n", level, &vaf);
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va_end(args);
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}
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/**
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* fscrypt_init() - Set up for fs encryption.
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*/
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static int __init fscrypt_init(void)
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{
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/*
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* Use an unbound workqueue to allow bios to be decrypted in parallel
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* even when they happen to complete on the same CPU. This sacrifices
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* locality, but it's worthwhile since decryption is CPU-intensive.
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*
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* Also use a high-priority workqueue to prioritize decryption work,
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* which blocks reads from completing, over regular application tasks.
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*/
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fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
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WQ_UNBOUND | WQ_HIGHPRI,
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num_online_cpus());
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if (!fscrypt_read_workqueue)
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goto fail;
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fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
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if (!fscrypt_ctx_cachep)
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goto fail_free_queue;
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fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
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if (!fscrypt_info_cachep)
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goto fail_free_ctx;
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|
|
return 0;
|
|
|
|
fail_free_ctx:
|
|
kmem_cache_destroy(fscrypt_ctx_cachep);
|
|
fail_free_queue:
|
|
destroy_workqueue(fscrypt_read_workqueue);
|
|
fail:
|
|
return -ENOMEM;
|
|
}
|
|
module_init(fscrypt_init)
|
|
|
|
/**
|
|
* fscrypt_exit() - Shutdown the fs encryption system
|
|
*/
|
|
static void __exit fscrypt_exit(void)
|
|
{
|
|
fscrypt_destroy();
|
|
|
|
if (fscrypt_read_workqueue)
|
|
destroy_workqueue(fscrypt_read_workqueue);
|
|
kmem_cache_destroy(fscrypt_ctx_cachep);
|
|
kmem_cache_destroy(fscrypt_info_cachep);
|
|
|
|
fscrypt_essiv_cleanup();
|
|
}
|
|
module_exit(fscrypt_exit);
|
|
|
|
MODULE_LICENSE("GPL");
|