kernel-ark/fs/ecryptfs/super.c
Roland Dreier 05dafedb90 ecryptfs: Remove unneeded locking that triggers lockdep false positives
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>
2009-09-23 09:10:30 -05:00

211 lines
6.4 KiB
C

/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 1997-2003 Erez Zadok
* Copyright (C) 2001-2003 Stony Brook University
* Copyright (C) 2004-2006 International Business Machines Corp.
* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
* Michael C. Thompson <mcthomps@us.ibm.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
* 02111-1307, USA.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/key.h>
#include <linux/seq_file.h>
#include <linux/smp_lock.h>
#include <linux/file.h>
#include <linux/crypto.h>
#include "ecryptfs_kernel.h"
struct kmem_cache *ecryptfs_inode_info_cache;
/**
* ecryptfs_alloc_inode - allocate an ecryptfs inode
* @sb: Pointer to the ecryptfs super block
*
* Called to bring an inode into existence.
*
* Only handle allocation, setting up structures should be done in
* ecryptfs_read_inode. This is because the kernel, between now and
* then, will 0 out the private data pointer.
*
* Returns a pointer to a newly allocated inode, NULL otherwise
*/
static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
{
struct ecryptfs_inode_info *inode_info;
struct inode *inode = NULL;
inode_info = kmem_cache_alloc(ecryptfs_inode_info_cache, GFP_KERNEL);
if (unlikely(!inode_info))
goto out;
ecryptfs_init_crypt_stat(&inode_info->crypt_stat);
mutex_init(&inode_info->lower_file_mutex);
inode_info->lower_file = NULL;
inode = &inode_info->vfs_inode;
out:
return inode;
}
/**
* ecryptfs_destroy_inode
* @inode: The ecryptfs inode
*
* This is used during the final destruction of the inode. All
* allocation of memory related to the inode, including allocated
* memory in the crypt_stat struct, will be released here. This
* function also fput()'s the persistent file for the lower inode.
* There should be no chance that this deallocation will be missed.
*/
static void ecryptfs_destroy_inode(struct inode *inode)
{
struct ecryptfs_inode_info *inode_info;
inode_info = ecryptfs_inode_to_private(inode);
if (inode_info->lower_file) {
struct dentry *lower_dentry =
inode_info->lower_file->f_dentry;
BUG_ON(!lower_dentry);
if (lower_dentry->d_inode) {
fput(inode_info->lower_file);
inode_info->lower_file = NULL;
d_drop(lower_dentry);
}
}
ecryptfs_destroy_crypt_stat(&inode_info->crypt_stat);
kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
}
/**
* ecryptfs_init_inode
* @inode: The ecryptfs inode
*
* Set up the ecryptfs inode.
*/
void ecryptfs_init_inode(struct inode *inode, struct inode *lower_inode)
{
ecryptfs_set_inode_lower(inode, lower_inode);
inode->i_ino = lower_inode->i_ino;
inode->i_version++;
inode->i_op = &ecryptfs_main_iops;
inode->i_fop = &ecryptfs_main_fops;
inode->i_mapping->a_ops = &ecryptfs_aops;
}
/**
* ecryptfs_put_super
* @sb: Pointer to the ecryptfs super block
*
* Final actions when unmounting a file system.
* This will handle deallocation and release of our private data.
*/
static void ecryptfs_put_super(struct super_block *sb)
{
struct ecryptfs_sb_info *sb_info = ecryptfs_superblock_to_private(sb);
lock_kernel();
ecryptfs_destroy_mount_crypt_stat(&sb_info->mount_crypt_stat);
kmem_cache_free(ecryptfs_sb_info_cache, sb_info);
ecryptfs_set_superblock_private(sb, NULL);
unlock_kernel();
}
/**
* ecryptfs_statfs
* @sb: The ecryptfs super block
* @buf: The struct kstatfs to fill in with stats
*
* Get the filesystem statistics. Currently, we let this pass right through
* to the lower filesystem and take no action ourselves.
*/
static int ecryptfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
return vfs_statfs(ecryptfs_dentry_to_lower(dentry), buf);
}
/**
* ecryptfs_clear_inode
* @inode - The ecryptfs inode
*
* Called by iput() when the inode reference count reached zero
* and the inode is not hashed anywhere. Used to clear anything
* that needs to be, before the inode is completely destroyed and put
* on the inode free list. We use this to drop out reference to the
* lower inode.
*/
static void ecryptfs_clear_inode(struct inode *inode)
{
iput(ecryptfs_inode_to_lower(inode));
}
/**
* ecryptfs_show_options
*
* Prints the mount options for a given superblock.
* Returns zero; does not fail.
*/
static int ecryptfs_show_options(struct seq_file *m, struct vfsmount *mnt)
{
struct super_block *sb = mnt->mnt_sb;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(sb)->mount_crypt_stat;
struct ecryptfs_global_auth_tok *walker;
mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
list_for_each_entry(walker,
&mount_crypt_stat->global_auth_tok_list,
mount_crypt_stat_list) {
if (walker->flags & ECRYPTFS_AUTH_TOK_FNEK)
seq_printf(m, ",ecryptfs_fnek_sig=%s", walker->sig);
else
seq_printf(m, ",ecryptfs_sig=%s", walker->sig);
}
mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
seq_printf(m, ",ecryptfs_cipher=%s",
mount_crypt_stat->global_default_cipher_name);
if (mount_crypt_stat->global_default_cipher_key_size)
seq_printf(m, ",ecryptfs_key_bytes=%zd",
mount_crypt_stat->global_default_cipher_key_size);
if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)
seq_printf(m, ",ecryptfs_passthrough");
if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
seq_printf(m, ",ecryptfs_xattr_metadata");
if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
seq_printf(m, ",ecryptfs_encrypted_view");
if (mount_crypt_stat->flags & ECRYPTFS_UNLINK_SIGS)
seq_printf(m, ",ecryptfs_unlink_sigs");
return 0;
}
const struct super_operations ecryptfs_sops = {
.alloc_inode = ecryptfs_alloc_inode,
.destroy_inode = ecryptfs_destroy_inode,
.drop_inode = generic_delete_inode,
.put_super = ecryptfs_put_super,
.statfs = ecryptfs_statfs,
.remount_fs = NULL,
.clear_inode = ecryptfs_clear_inode,
.show_options = ecryptfs_show_options
};