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![Jaegeuk Kim](/assets/img/avatar_default.png)
As Al pointed, d_revalidate should return RCU lookup before using d_inode.
This was originally introduced by:
commit 34286d6662
("fs: rcu-walk aware d_revalidate method").
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: stable <stable@vger.kernel.org>
568 lines
15 KiB
C
568 lines
15 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/bio.h>
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#include <linux/dcache.h>
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#include <linux/namei.h>
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#include <linux/fscrypto.h>
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#include <linux/ecryptfs.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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/**
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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_WRITE_PATH_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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* @inode: The inode for which we are doing the crypto
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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: An allocated and initialized encryption context on success; error
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* value or NULL otherwise.
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*/
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struct fscrypt_ctx *fscrypt_get_ctx(struct inode *inode, gfp_t gfp_flags)
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{
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struct fscrypt_ctx *ctx = NULL;
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struct fscrypt_info *ci = inode->i_crypt_info;
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unsigned long flags;
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if (ci == NULL)
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return ERR_PTR(-ENOKEY);
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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_WRITE_PATH_FL;
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return ctx;
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}
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EXPORT_SYMBOL(fscrypt_get_ctx);
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/**
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* fscrypt_complete() - The completion callback for page encryption
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* @req: The asynchronous encryption request context
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* @res: The result of the encryption operation
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*/
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static void fscrypt_complete(struct crypto_async_request *req, int res)
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{
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struct fscrypt_completion_result *ecr = req->data;
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if (res == -EINPROGRESS)
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return;
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ecr->res = res;
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complete(&ecr->completion);
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}
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typedef enum {
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FS_DECRYPT = 0,
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FS_ENCRYPT,
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} fscrypt_direction_t;
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static int do_page_crypto(struct inode *inode,
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fscrypt_direction_t rw, pgoff_t index,
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struct page *src_page, struct page *dest_page,
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gfp_t gfp_flags)
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{
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u8 xts_tweak[FS_XTS_TWEAK_SIZE];
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struct skcipher_request *req = NULL;
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DECLARE_FS_COMPLETION_RESULT(ecr);
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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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req = skcipher_request_alloc(tfm, gfp_flags);
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if (!req) {
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printk_ratelimited(KERN_ERR
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"%s: crypto_request_alloc() failed\n",
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__func__);
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return -ENOMEM;
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}
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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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fscrypt_complete, &ecr);
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BUILD_BUG_ON(FS_XTS_TWEAK_SIZE < sizeof(index));
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memcpy(xts_tweak, &index, sizeof(index));
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memset(&xts_tweak[sizeof(index)], 0,
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FS_XTS_TWEAK_SIZE - sizeof(index));
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sg_init_table(&dst, 1);
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sg_set_page(&dst, dest_page, PAGE_SIZE, 0);
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sg_init_table(&src, 1);
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sg_set_page(&src, src_page, PAGE_SIZE, 0);
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skcipher_request_set_crypt(req, &src, &dst, PAGE_SIZE,
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xts_tweak);
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if (rw == FS_DECRYPT)
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res = crypto_skcipher_decrypt(req);
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else
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res = crypto_skcipher_encrypt(req);
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if (res == -EINPROGRESS || res == -EBUSY) {
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BUG_ON(req->base.data != &ecr);
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wait_for_completion(&ecr.completion);
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res = ecr.res;
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}
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skcipher_request_free(req);
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if (res) {
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printk_ratelimited(KERN_ERR
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"%s: crypto_skcipher_encrypt() returned %d\n",
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__func__, 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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static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, 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_WRITE_PATH_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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* @plaintext_page: The page to encrypt. Must be locked.
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* @gfp_flags: The gfp flag for memory allocation
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*
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* Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
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* encryption context.
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*
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* Called on the page write path. 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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* Return: An allocated 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(struct inode *inode,
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struct page *plaintext_page, gfp_t gfp_flags)
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{
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struct fscrypt_ctx *ctx;
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struct page *ciphertext_page = NULL;
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int err;
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BUG_ON(!PageLocked(plaintext_page));
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ctx = fscrypt_get_ctx(inode, gfp_flags);
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if (IS_ERR(ctx))
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return (struct page *)ctx;
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/* The encryption operation will require a bounce page. */
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ciphertext_page = 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 = plaintext_page;
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err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index,
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plaintext_page, ciphertext_page,
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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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* f2crypt_decrypt_page() - Decrypts a page in-place
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* @page: The page to decrypt. Must be locked.
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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(struct page *page)
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{
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BUG_ON(!PageLocked(page));
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return do_page_crypto(page->mapping->host,
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FS_DECRYPT, page->index, page, page, GFP_NOFS);
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}
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EXPORT_SYMBOL(fscrypt_decrypt_page);
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int fscrypt_zeroout_range(struct inode *inode, pgoff_t lblk,
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sector_t pblk, unsigned int len)
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{
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struct fscrypt_ctx *ctx;
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struct page *ciphertext_page = NULL;
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struct bio *bio;
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int ret, err = 0;
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BUG_ON(inode->i_sb->s_blocksize != PAGE_SIZE);
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ctx = fscrypt_get_ctx(inode, GFP_NOFS);
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if (IS_ERR(ctx))
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return PTR_ERR(ctx);
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ciphertext_page = alloc_bounce_page(ctx, GFP_NOWAIT);
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if (IS_ERR(ciphertext_page)) {
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err = PTR_ERR(ciphertext_page);
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goto errout;
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}
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while (len--) {
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err = do_page_crypto(inode, FS_ENCRYPT, lblk,
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ZERO_PAGE(0), ciphertext_page,
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GFP_NOFS);
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if (err)
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goto errout;
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bio = bio_alloc(GFP_NOWAIT, 1);
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if (!bio) {
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err = -ENOMEM;
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goto errout;
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}
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bio->bi_bdev = inode->i_sb->s_bdev;
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bio->bi_iter.bi_sector =
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pblk << (inode->i_sb->s_blocksize_bits - 9);
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ret = bio_add_page(bio, ciphertext_page,
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inode->i_sb->s_blocksize, 0);
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if (ret != inode->i_sb->s_blocksize) {
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/* should never happen! */
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WARN_ON(1);
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bio_put(bio);
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err = -EIO;
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goto errout;
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}
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err = submit_bio_wait(WRITE, bio);
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if ((err == 0) && bio->bi_error)
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err = -EIO;
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bio_put(bio);
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if (err)
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goto errout;
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lblk++;
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pblk++;
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}
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err = 0;
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errout:
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fscrypt_release_ctx(ctx);
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return err;
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}
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EXPORT_SYMBOL(fscrypt_zeroout_range);
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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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struct fscrypt_info *ci;
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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 (!d_inode(dir)->i_sb->s_cop->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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ci = d_inode(dir)->i_crypt_info;
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if (ci && ci->ci_keyring_key &&
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(ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
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(1 << KEY_FLAG_REVOKED) |
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(1 << KEY_FLAG_DEAD))))
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ci = NULL;
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/* this should eventually be an flag in d_flags */
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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 = (ci != NULL);
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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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EXPORT_SYMBOL(fscrypt_d_ops);
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/*
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* Call fscrypt_decrypt_page on every single page, reusing the encryption
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* context.
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*/
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static void completion_pages(struct work_struct *work)
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{
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struct fscrypt_ctx *ctx =
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container_of(work, struct fscrypt_ctx, r.work);
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struct bio *bio = ctx->r.bio;
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struct bio_vec *bv;
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int i;
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bio_for_each_segment_all(bv, bio, i) {
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struct page *page = bv->bv_page;
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int ret = fscrypt_decrypt_page(page);
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if (ret) {
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WARN_ON_ONCE(1);
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SetPageError(page);
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} else {
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SetPageUptodate(page);
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}
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unlock_page(page);
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}
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fscrypt_release_ctx(ctx);
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bio_put(bio);
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}
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void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
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{
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INIT_WORK(&ctx->r.work, completion_pages);
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ctx->r.bio = bio;
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queue_work(fscrypt_read_workqueue, &ctx->r.work);
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}
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EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
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void fscrypt_pullback_bio_page(struct page **page, bool restore)
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{
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struct fscrypt_ctx *ctx;
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struct page *bounce_page;
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/* The bounce data pages are unmapped. */
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if ((*page)->mapping)
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return;
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/* The bounce data page is unmapped. */
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bounce_page = *page;
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ctx = (struct fscrypt_ctx *)page_private(bounce_page);
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/* restore control page */
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*page = ctx->w.control_page;
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if (restore)
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fscrypt_restore_control_page(bounce_page);
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}
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EXPORT_SYMBOL(fscrypt_pullback_bio_page);
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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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*
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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.
|
|
*/
|
|
int fscrypt_initialize(void)
|
|
{
|
|
int i, res = -ENOMEM;
|
|
|
|
if (fscrypt_bounce_page_pool)
|
|
return 0;
|
|
|
|
mutex_lock(&fscrypt_init_mutex);
|
|
if (fscrypt_bounce_page_pool)
|
|
goto already_initialized;
|
|
|
|
for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
|
|
struct fscrypt_ctx *ctx;
|
|
|
|
ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
|
|
if (!ctx)
|
|
goto fail;
|
|
list_add(&ctx->free_list, &fscrypt_free_ctxs);
|
|
}
|
|
|
|
fscrypt_bounce_page_pool =
|
|
mempool_create_page_pool(num_prealloc_crypto_pages, 0);
|
|
if (!fscrypt_bounce_page_pool)
|
|
goto fail;
|
|
|
|
already_initialized:
|
|
mutex_unlock(&fscrypt_init_mutex);
|
|
return 0;
|
|
fail:
|
|
fscrypt_destroy();
|
|
mutex_unlock(&fscrypt_init_mutex);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_initialize);
|
|
|
|
/**
|
|
* fscrypt_init() - Set up for fs encryption.
|
|
*/
|
|
static int __init fscrypt_init(void)
|
|
{
|
|
fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
|
|
WQ_HIGHPRI, 0);
|
|
if (!fscrypt_read_workqueue)
|
|
goto fail;
|
|
|
|
fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
|
|
if (!fscrypt_ctx_cachep)
|
|
goto fail_free_queue;
|
|
|
|
fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
|
|
if (!fscrypt_info_cachep)
|
|
goto fail_free_ctx;
|
|
|
|
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);
|
|
}
|
|
module_exit(fscrypt_exit);
|
|
|
|
MODULE_LICENSE("GPL");
|