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authorRoland Dreier <roland@digitalvampire.org>2009-07-14 13:32:56 -0700
committerTyler Hicks <tyhicks@linux.vnet.ibm.com>2009-09-23 09:10:30 -0500
commit05dafedb906425fe935199f4c92700d87285e3e9 (patch)
tree7f3162455188c322baf9c6ca9a2890394380201d /fs/ecryptfs/super.c
parent94e0fb086fc5663c38bbc0fe86d698be8314f82f (diff)
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>
Diffstat (limited to 'fs/ecryptfs/super.c')
-rw-r--r--fs/ecryptfs/super.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/fs/ecryptfs/super.c b/fs/ecryptfs/super.c
index 12d649602d3..b15a43a80ab 100644
--- a/fs/ecryptfs/super.c
+++ b/fs/ecryptfs/super.c
@@ -77,7 +77,6 @@ static void ecryptfs_destroy_inode(struct inode *inode)
struct ecryptfs_inode_info *inode_info;
inode_info = ecryptfs_inode_to_private(inode);
- mutex_lock(&inode_info->lower_file_mutex);
if (inode_info->lower_file) {
struct dentry *lower_dentry =
inode_info->lower_file->f_dentry;
@@ -89,7 +88,6 @@ static void ecryptfs_destroy_inode(struct inode *inode)
d_drop(lower_dentry);
}
}
- mutex_unlock(&inode_info->lower_file_mutex);
ecryptfs_destroy_crypt_stat(&inode_info->crypt_stat);
kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
}