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![Roland Dreier](/assets/img/avatar_default.png)
In ecryptfs_destroy_inode(), inode_info->lower_file_mutex is locked, and just after the mutex is unlocked, the code does: kmem_cache_free(ecryptfs_inode_info_cache, inode_info); This means that if another context could possibly try to take the same mutex as ecryptfs_destroy_inode(), then it could end up getting the mutex just before the data structure containing the mutex is freed. So any such use would be an obvious use-after-free bug (catchable with slab poisoning or mutex debugging), and therefore the locking in ecryptfs_destroy_inode() is not needed and can be dropped. Similarly, in ecryptfs_destroy_crypt_stat(), crypt_stat->keysig_list_mutex is locked, and then the mutex is unlocked just before the code does: memset(crypt_stat, 0, sizeof(struct ecryptfs_crypt_stat)); Therefore taking this mutex is similarly not necessary. Removing this locking fixes false-positive lockdep reports such as the following (and they are false-positives for exactly the same reason that the locking is not needed): ================================= [ INFO: inconsistent lock state ] 2.6.31-2-generic #14~rbd3 --------------------------------- inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage. kswapd0/323 [HC0[0]:SC0[0]:HE1:SE1] takes: (&inode_info->lower_file_mutex){+.+.?.}, at: [<ffffffff81210d34>] ecryptfs_destroy_inode+0x34/0x100 {RECLAIM_FS-ON-W} state was registered at: [<ffffffff8108c02c>] mark_held_locks+0x6c/0xa0 [<ffffffff8108c10f>] lockdep_trace_alloc+0xaf/0xe0 [<ffffffff81125a51>] kmem_cache_alloc+0x41/0x1a0 [<ffffffff8113117a>] get_empty_filp+0x7a/0x1a0 [<ffffffff8112dd46>] dentry_open+0x36/0xc0 [<ffffffff8121a36c>] ecryptfs_privileged_open+0x5c/0x2e0 [<ffffffff81210283>] ecryptfs_init_persistent_file+0xa3/0xe0 [<ffffffff8120e838>] ecryptfs_lookup_and_interpose_lower+0x278/0x380 [<ffffffff8120f97a>] ecryptfs_lookup+0x12a/0x250 [<ffffffff8113930a>] real_lookup+0xea/0x160 [<ffffffff8113afc8>] do_lookup+0xb8/0xf0 [<ffffffff8113b518>] __link_path_walk+0x518/0x870 [<ffffffff8113bd9c>] path_walk+0x5c/0xc0 [<ffffffff8113be5b>] do_path_lookup+0x5b/0xa0 [<ffffffff8113bfe7>] user_path_at+0x57/0xa0 [<ffffffff811340dc>] vfs_fstatat+0x3c/0x80 [<ffffffff8113424b>] vfs_stat+0x1b/0x20 [<ffffffff81134274>] sys_newstat+0x24/0x50 [<ffffffff81013132>] system_call_fastpath+0x16/0x1b [<ffffffffffffffff>] 0xffffffffffffffff irq event stamp: 7811 hardirqs last enabled at (7811): [<ffffffff810c037f>] call_rcu+0x5f/0x90 hardirqs last disabled at (7810): [<ffffffff810c0353>] call_rcu+0x33/0x90 softirqs last enabled at (3764): [<ffffffff810631da>] __do_softirq+0x14a/0x220 softirqs last disabled at (3751): [<ffffffff8101440c>] call_softirq+0x1c/0x30 other info that might help us debug this: 2 locks held by kswapd0/323: #0: (shrinker_rwsem){++++..}, at: [<ffffffff810f67ed>] shrink_slab+0x3d/0x190 #1: (&type->s_umount_key#35){.+.+..}, at: [<ffffffff811429a1>] prune_dcache+0xd1/0x1b0 stack backtrace: Pid: 323, comm: kswapd0 Tainted: G C 2.6.31-2-generic #14~rbd3 Call Trace: [<ffffffff8108ad6c>] print_usage_bug+0x18c/0x1a0 [<ffffffff8108aff0>] ? check_usage_forwards+0x0/0xc0 [<ffffffff8108bac2>] mark_lock_irq+0xf2/0x280 [<ffffffff8108bd87>] mark_lock+0x137/0x1d0 [<ffffffff81164710>] ? fsnotify_clear_marks_by_inode+0x30/0xf0 [<ffffffff8108bee6>] mark_irqflags+0xc6/0x1a0 [<ffffffff8108d337>] __lock_acquire+0x287/0x430 [<ffffffff8108d585>] lock_acquire+0xa5/0x150 [<ffffffff81210d34>] ? ecryptfs_destroy_inode+0x34/0x100 [<ffffffff8108d2e7>] ? __lock_acquire+0x237/0x430 [<ffffffff815526ad>] __mutex_lock_common+0x4d/0x3d0 [<ffffffff81210d34>] ? ecryptfs_destroy_inode+0x34/0x100 [<ffffffff81164710>] ? fsnotify_clear_marks_by_inode+0x30/0xf0 [<ffffffff81210d34>] ? ecryptfs_destroy_inode+0x34/0x100 [<ffffffff8129a91e>] ? _raw_spin_unlock+0x5e/0xb0 [<ffffffff81552b36>] mutex_lock_nested+0x46/0x60 [<ffffffff81210d34>] ecryptfs_destroy_inode+0x34/0x100 [<ffffffff81145d27>] destroy_inode+0x87/0xd0 [<ffffffff81146b4c>] generic_delete_inode+0x12c/0x1a0 [<ffffffff81145832>] iput+0x62/0x70 [<ffffffff811423c8>] dentry_iput+0x98/0x110 [<ffffffff81142550>] d_kill+0x50/0x80 [<ffffffff81142623>] prune_one_dentry+0xa3/0xc0 [<ffffffff811428b1>] __shrink_dcache_sb+0x271/0x290 [<ffffffff811429d9>] prune_dcache+0x109/0x1b0 [<ffffffff81142abf>] shrink_dcache_memory+0x3f/0x50 [<ffffffff810f68dd>] shrink_slab+0x12d/0x190 [<ffffffff810f9377>] balance_pgdat+0x4d7/0x640 [<ffffffff8104c4c0>] ? finish_task_switch+0x40/0x150 [<ffffffff810f63c0>] ? isolate_pages_global+0x0/0x60 [<ffffffff810f95f7>] kswapd+0x117/0x170 [<ffffffff810777a0>] ? autoremove_wake_function+0x0/0x40 [<ffffffff810f94e0>] ? kswapd+0x0/0x170 [<ffffffff810773be>] kthread+0x9e/0xb0 [<ffffffff8101430a>] child_rip+0xa/0x20 [<ffffffff81013c90>] ? restore_args+0x0/0x30 [<ffffffff81077320>] ? kthread+0x0/0xb0 [<ffffffff81014300>] ? child_rip+0x0/0x20 Signed-off-by: Roland Dreier <roland@digitalvampire.org> Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
210 lines
6.4 KiB
C
210 lines
6.4 KiB
C
/**
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* eCryptfs: Linux filesystem encryption layer
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*
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* Copyright (C) 1997-2003 Erez Zadok
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* Copyright (C) 2001-2003 Stony Brook University
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* Copyright (C) 2004-2006 International Business Machines Corp.
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* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
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* Michael C. Thompson <mcthomps@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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* 02111-1307, USA.
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*/
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/key.h>
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#include <linux/seq_file.h>
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#include <linux/smp_lock.h>
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#include <linux/file.h>
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#include <linux/crypto.h>
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#include "ecryptfs_kernel.h"
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struct kmem_cache *ecryptfs_inode_info_cache;
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/**
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* ecryptfs_alloc_inode - allocate an ecryptfs inode
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* @sb: Pointer to the ecryptfs super block
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*
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* Called to bring an inode into existence.
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*
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* Only handle allocation, setting up structures should be done in
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* ecryptfs_read_inode. This is because the kernel, between now and
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* then, will 0 out the private data pointer.
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*
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* Returns a pointer to a newly allocated inode, NULL otherwise
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*/
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static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
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{
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struct ecryptfs_inode_info *inode_info;
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struct inode *inode = NULL;
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inode_info = kmem_cache_alloc(ecryptfs_inode_info_cache, GFP_KERNEL);
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if (unlikely(!inode_info))
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goto out;
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ecryptfs_init_crypt_stat(&inode_info->crypt_stat);
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mutex_init(&inode_info->lower_file_mutex);
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inode_info->lower_file = NULL;
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inode = &inode_info->vfs_inode;
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out:
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return inode;
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}
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/**
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* ecryptfs_destroy_inode
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* @inode: The ecryptfs inode
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*
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* This is used during the final destruction of the inode. All
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* allocation of memory related to the inode, including allocated
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* memory in the crypt_stat struct, will be released here. This
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* function also fput()'s the persistent file for the lower inode.
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* There should be no chance that this deallocation will be missed.
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*/
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static void ecryptfs_destroy_inode(struct inode *inode)
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{
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struct ecryptfs_inode_info *inode_info;
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inode_info = ecryptfs_inode_to_private(inode);
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if (inode_info->lower_file) {
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struct dentry *lower_dentry =
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inode_info->lower_file->f_dentry;
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BUG_ON(!lower_dentry);
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if (lower_dentry->d_inode) {
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fput(inode_info->lower_file);
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inode_info->lower_file = NULL;
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d_drop(lower_dentry);
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}
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}
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ecryptfs_destroy_crypt_stat(&inode_info->crypt_stat);
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kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
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}
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/**
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* ecryptfs_init_inode
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* @inode: The ecryptfs inode
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*
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* Set up the ecryptfs inode.
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*/
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void ecryptfs_init_inode(struct inode *inode, struct inode *lower_inode)
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{
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ecryptfs_set_inode_lower(inode, lower_inode);
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inode->i_ino = lower_inode->i_ino;
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inode->i_version++;
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inode->i_op = &ecryptfs_main_iops;
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inode->i_fop = &ecryptfs_main_fops;
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inode->i_mapping->a_ops = &ecryptfs_aops;
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}
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/**
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* ecryptfs_put_super
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* @sb: Pointer to the ecryptfs super block
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*
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* Final actions when unmounting a file system.
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* This will handle deallocation and release of our private data.
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*/
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static void ecryptfs_put_super(struct super_block *sb)
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{
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struct ecryptfs_sb_info *sb_info = ecryptfs_superblock_to_private(sb);
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lock_kernel();
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ecryptfs_destroy_mount_crypt_stat(&sb_info->mount_crypt_stat);
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kmem_cache_free(ecryptfs_sb_info_cache, sb_info);
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ecryptfs_set_superblock_private(sb, NULL);
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unlock_kernel();
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}
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/**
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* ecryptfs_statfs
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* @sb: The ecryptfs super block
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* @buf: The struct kstatfs to fill in with stats
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*
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* Get the filesystem statistics. Currently, we let this pass right through
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* to the lower filesystem and take no action ourselves.
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*/
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static int ecryptfs_statfs(struct dentry *dentry, struct kstatfs *buf)
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{
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return vfs_statfs(ecryptfs_dentry_to_lower(dentry), buf);
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}
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/**
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* ecryptfs_clear_inode
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* @inode - The ecryptfs inode
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*
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* Called by iput() when the inode reference count reached zero
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* and the inode is not hashed anywhere. Used to clear anything
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* that needs to be, before the inode is completely destroyed and put
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* on the inode free list. We use this to drop out reference to the
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* lower inode.
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*/
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static void ecryptfs_clear_inode(struct inode *inode)
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{
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iput(ecryptfs_inode_to_lower(inode));
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}
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/**
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* ecryptfs_show_options
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*
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* Prints the mount options for a given superblock.
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* Returns zero; does not fail.
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*/
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static int ecryptfs_show_options(struct seq_file *m, struct vfsmount *mnt)
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{
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struct super_block *sb = mnt->mnt_sb;
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struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
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&ecryptfs_superblock_to_private(sb)->mount_crypt_stat;
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struct ecryptfs_global_auth_tok *walker;
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mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
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list_for_each_entry(walker,
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&mount_crypt_stat->global_auth_tok_list,
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mount_crypt_stat_list) {
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if (walker->flags & ECRYPTFS_AUTH_TOK_FNEK)
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seq_printf(m, ",ecryptfs_fnek_sig=%s", walker->sig);
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else
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seq_printf(m, ",ecryptfs_sig=%s", walker->sig);
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}
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mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
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seq_printf(m, ",ecryptfs_cipher=%s",
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mount_crypt_stat->global_default_cipher_name);
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if (mount_crypt_stat->global_default_cipher_key_size)
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seq_printf(m, ",ecryptfs_key_bytes=%zd",
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mount_crypt_stat->global_default_cipher_key_size);
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if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)
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seq_printf(m, ",ecryptfs_passthrough");
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if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
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seq_printf(m, ",ecryptfs_xattr_metadata");
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if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
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seq_printf(m, ",ecryptfs_encrypted_view");
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if (mount_crypt_stat->flags & ECRYPTFS_UNLINK_SIGS)
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seq_printf(m, ",ecryptfs_unlink_sigs");
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return 0;
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}
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const struct super_operations ecryptfs_sops = {
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.alloc_inode = ecryptfs_alloc_inode,
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.destroy_inode = ecryptfs_destroy_inode,
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.drop_inode = generic_delete_inode,
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.put_super = ecryptfs_put_super,
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.statfs = ecryptfs_statfs,
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.remount_fs = NULL,
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.clear_inode = ecryptfs_clear_inode,
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.show_options = ecryptfs_show_options
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};
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