q3k
/
linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
linux/fs/ecryptfs
History
Roland Dreier aa06117f19 eCryptfs: Fix lockdep-reported AB-BA mutex issue 
Lockdep reports the following valid-looking possible AB-BA deadlock with
global_auth_tok_list_mutex and keysig_list_mutex:

  ecryptfs_new_file_context() ->
      ecryptfs_copy_mount_wide_sigs_to_inode_sigs() ->
          mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
          -> ecryptfs_add_keysig() ->
              mutex_lock(&crypt_stat->keysig_list_mutex);

vs

  ecryptfs_generate_key_packet_set() ->
      mutex_lock(&crypt_stat->keysig_list_mutex);
      -> ecryptfs_find_global_auth_tok_for_sig() ->
          mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);

ie the two mutexes are taken in opposite orders in the two different
code paths.  I'm not sure if this is a real bug where two threads could
actually hit the two paths in parallel and deadlock, but it at least
makes lockdep impossible to use with ecryptfs since this report triggers
every time and disables future lockdep reporting.

Since ecryptfs_add_keysig() is called only from the single callsite in
ecryptfs_copy_mount_wide_sigs_to_inode_sigs(), the simplest fix seems to
be to move the lock of keysig_list_mutex back up outside of the where
global_auth_tok_list_mutex is taken.  This patch does that, and fixes
the lockdep report on my system (and ecryptfs still works OK).

The full output of lockdep fixed by this patch is:

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.31-2-generic #14~rbd2
-------------------------------------------------------
gdm/2640 is trying to acquire lock:
 (&mount_crypt_stat->global_auth_tok_list_mutex){+.+.+.}, at: [<ffffffff8121591e>] ecryptfs_find_global_auth_tok_for_sig+0x2e/0x90

but task is already holding lock:
 (&crypt_stat->keysig_list_mutex){+.+.+.}, at: [<ffffffff81217728>] ecryptfs_generate_key_packet_set+0x58/0x2b0

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&crypt_stat->keysig_list_mutex){+.+.+.}:
       [<ffffffff8108c897>] check_prev_add+0x2a7/0x370
       [<ffffffff8108cfc1>] validate_chain+0x661/0x750
       [<ffffffff8108d2e7>] __lock_acquire+0x237/0x430
       [<ffffffff8108d585>] lock_acquire+0xa5/0x150
       [<ffffffff815526cd>] __mutex_lock_common+0x4d/0x3d0
       [<ffffffff81552b56>] mutex_lock_nested+0x46/0x60
       [<ffffffff8121526a>] ecryptfs_add_keysig+0x5a/0xb0
       [<ffffffff81213299>] ecryptfs_copy_mount_wide_sigs_to_inode_sigs+0x59/0xb0
       [<ffffffff81214b06>] ecryptfs_new_file_context+0xa6/0x1a0
       [<ffffffff8120e42a>] ecryptfs_initialize_file+0x4a/0x140
       [<ffffffff8120e54d>] ecryptfs_create+0x2d/0x60
       [<ffffffff8113a7d4>] vfs_create+0xb4/0xe0
       [<ffffffff8113a8c4>] __open_namei_create+0xc4/0x110
       [<ffffffff8113d1c1>] do_filp_open+0xa01/0xae0
       [<ffffffff8112d8d9>] do_sys_open+0x69/0x140
       [<ffffffff8112d9f0>] sys_open+0x20/0x30
       [<ffffffff81013132>] system_call_fastpath+0x16/0x1b
       [<ffffffffffffffff>] 0xffffffffffffffff

-> #0 (&mount_crypt_stat->global_auth_tok_list_mutex){+.+.+.}:
       [<ffffffff8108c675>] check_prev_add+0x85/0x370
       [<ffffffff8108cfc1>] validate_chain+0x661/0x750
       [<ffffffff8108d2e7>] __lock_acquire+0x237/0x430
       [<ffffffff8108d585>] lock_acquire+0xa5/0x150
       [<ffffffff815526cd>] __mutex_lock_common+0x4d/0x3d0
       [<ffffffff81552b56>] mutex_lock_nested+0x46/0x60
       [<ffffffff8121591e>] ecryptfs_find_global_auth_tok_for_sig+0x2e/0x90
       [<ffffffff812177d5>] ecryptfs_generate_key_packet_set+0x105/0x2b0
       [<ffffffff81212f49>] ecryptfs_write_headers_virt+0xc9/0x120
       [<ffffffff8121306d>] ecryptfs_write_metadata+0xcd/0x200
       [<ffffffff8120e44b>] ecryptfs_initialize_file+0x6b/0x140
       [<ffffffff8120e54d>] ecryptfs_create+0x2d/0x60
       [<ffffffff8113a7d4>] vfs_create+0xb4/0xe0
       [<ffffffff8113a8c4>] __open_namei_create+0xc4/0x110
       [<ffffffff8113d1c1>] do_filp_open+0xa01/0xae0
       [<ffffffff8112d8d9>] do_sys_open+0x69/0x140
       [<ffffffff8112d9f0>] sys_open+0x20/0x30
       [<ffffffff81013132>] system_call_fastpath+0x16/0x1b
       [<ffffffffffffffff>] 0xffffffffffffffff

other info that might help us debug this:

2 locks held by gdm/2640:
 #0:  (&sb->s_type->i_mutex_key#11){+.+.+.}, at: [<ffffffff8113cb8b>] do_filp_open+0x3cb/0xae0
 #1:  (&crypt_stat->keysig_list_mutex){+.+.+.}, at: [<ffffffff81217728>] ecryptfs_generate_key_packet_set+0x58/0x2b0

stack backtrace:
Pid: 2640, comm: gdm Tainted: G         C 2.6.31-2-generic #14~rbd2
Call Trace:
 [<ffffffff8108b988>] print_circular_bug_tail+0xa8/0xf0
 [<ffffffff8108c675>] check_prev_add+0x85/0x370
 [<ffffffff81094912>] ? __module_text_address+0x12/0x60
 [<ffffffff8108cfc1>] validate_chain+0x661/0x750
 [<ffffffff81017275>] ? print_context_stack+0x85/0x140
 [<ffffffff81089c68>] ? find_usage_backwards+0x38/0x160
 [<ffffffff8108d2e7>] __lock_acquire+0x237/0x430
 [<ffffffff8108d585>] lock_acquire+0xa5/0x150
 [<ffffffff8121591e>] ? ecryptfs_find_global_auth_tok_for_sig+0x2e/0x90
 [<ffffffff8108b0b0>] ? check_usage_backwards+0x0/0xb0
 [<ffffffff815526cd>] __mutex_lock_common+0x4d/0x3d0
 [<ffffffff8121591e>] ? ecryptfs_find_global_auth_tok_for_sig+0x2e/0x90
 [<ffffffff8121591e>] ? ecryptfs_find_global_auth_tok_for_sig+0x2e/0x90
 [<ffffffff8108c02c>] ? mark_held_locks+0x6c/0xa0
 [<ffffffff81125b0d>] ? kmem_cache_alloc+0xfd/0x1a0
 [<ffffffff8108c34d>] ? trace_hardirqs_on_caller+0x14d/0x190
 [<ffffffff81552b56>] mutex_lock_nested+0x46/0x60
 [<ffffffff8121591e>] ecryptfs_find_global_auth_tok_for_sig+0x2e/0x90
 [<ffffffff812177d5>] ecryptfs_generate_key_packet_set+0x105/0x2b0
 [<ffffffff81212f49>] ecryptfs_write_headers_virt+0xc9/0x120
 [<ffffffff8121306d>] ecryptfs_write_metadata+0xcd/0x200
 [<ffffffff81210240>] ? ecryptfs_init_persistent_file+0x60/0xe0
 [<ffffffff8120e44b>] ecryptfs_initialize_file+0x6b/0x140
 [<ffffffff8120e54d>] ecryptfs_create+0x2d/0x60
 [<ffffffff8113a7d4>] vfs_create+0xb4/0xe0
 [<ffffffff8113a8c4>] __open_namei_create+0xc4/0x110
 [<ffffffff8113d1c1>] do_filp_open+0xa01/0xae0
 [<ffffffff8129a93e>] ? _raw_spin_unlock+0x5e/0xb0
 [<ffffffff8155410b>] ? _spin_unlock+0x2b/0x40
 [<ffffffff81139e9b>] ? getname+0x3b/0x240
 [<ffffffff81148a5a>] ? alloc_fd+0xfa/0x140
 [<ffffffff8112d8d9>] do_sys_open+0x69/0x140
 [<ffffffff81553b8f>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 [<ffffffff8112d9f0>] sys_open+0x20/0x30
 [<ffffffff81013132>] system_call_fastpath+0x16/0x1b

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
 		2009-09-23 09:10:30 -05:00
..
Kconfig fs/Kconfig: move ecryptfs out 2009-01-22 13:15:56 +03:00
Makefile eCryptfs: remove netlink transport 2008-10-16 11:21:39 -07:00
crypto.c eCryptfs: Fix lockdep-reported AB-BA mutex issue 2009-09-23 09:10:30 -05:00
debug.c eCryptfs: update comment and debug statement 2007-10-16 09:43:11 -07:00
dentry.c constify dentry_operations: ecryptfs 2009-03-27 14:44:01 -04:00
ecryptfs_kernel.h const: mark remaining address_space_operations const 2009-09-22 07:17:24 -07:00
file.c eCryptfs: Fix data types (int/size_t) 2009-01-06 15:59:22 -08:00
inode.c eCryptfs: Fix min function comparison warning 2009-04-27 13:31:12 -05:00
keystore.c eCryptfs: Fix lockdep-reported AB-BA mutex issue 2009-09-23 09:10:30 -05:00
kthread.c CRED: Pass credentials through dentry_open() 2008-11-14 10:39:22 +11:00
main.c Convert obvious places to deactivate_locked_super() 2009-05-09 10:49:40 -04:00
messaging.c eCryptfs: NULL pointer dereference in ecryptfs_send_miscdev() 2009-04-22 03:54:13 -05:00
miscdev.c eCryptfs: NULL pointer dereference in ecryptfs_send_miscdev() 2009-04-22 03:54:13 -05:00
mmap.c const: mark remaining address_space_operations const 2009-09-22 07:17:24 -07:00
read_write.c eCryptfs: Fix data corruption when using ecryptfs_passthrough 2009-04-22 03:54:13 -05:00
super.c ecryptfs: Remove unneeded locking that triggers lockdep false positives 2009-09-23 09:10:30 -05:00