From a19350097200570571aa522afebb96b34db534f4 Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Date: Thu, 14 Feb 2013 09:07:36 +0200
Subject: [PATCH] selinux: do not confuse lockdep

Selinux has per-inode mutexes called 'isec->lock', and they are initialized in
the same place, which makes lockdep treat all of the them as if they were
identical. However, locking rules may be a little bit different depending on
the file-system, so we should put these locks to separate classes, just like we
do for 'i_mutex'. Namely, we should put them to per-FS type classes, which is
exactly what this patch does.

The problem this patch intends to fix is a strange lockdep warning, which I,
frankly speaking, do not really understand, but I believe the root-cause should
be fixed by this patch.

Look at the stacktrace #4: here we have 'debugfs_create_dir()'

[    5.390312] ======================================================
[    5.396500] [ INFO: possible circular locking dependency detected ]
[    5.402781] 3.8.0-rc6-00005-g4f7e39d #49 Not tainted
[    5.407750] -------------------------------------------------------
[    5.414031] systemd/1 is trying to acquire lock:
[    5.418656]  (&c->tnc_mutex){+.+...}, at: [<c01552d0>] ubifs_tnc_locate+0x30/0x198
[    5.426343]
[    5.426343] but task is already holding lock:
[    5.432218]  (&isec->lock){+.+.+.}, at: [<c018e298>] inode_doinit_with_dentry+0x8c/0x55c
[    5.440375]
[    5.440375] which lock already depends on the new lock.
[    5.440375]
[    5.448593]
[    5.448593] the existing dependency chain (in reverse order) is:
[    5.456093]
-> #4 (&isec->lock){+.+.+.}:
[    5.460250]        [<c004e8e8>] lock_acquire+0x64/0x78
[    5.465437]        [<c0355d5c>] mutex_lock_nested+0x5c/0x2ec
[    5.471125]        [<c018e298>] inode_doinit_with_dentry+0x8c/0x55c
[    5.477437]        [<c0189bd8>] security_d_instantiate+0x1c/0x34
[    5.483500]        [<c017a614>] debugfs_mknod.part.15.constprop.18+0x94/0x128
[    5.490656]        [<c017a858>] __create_file+0x1b0/0x25c
[    5.496093]        [<c017a98c>] debugfs_create_dir+0x1c/0x28
[    5.501781]        [<c0491ce8>] pinctrl_init+0x1c/0xd0
[    5.506968]        [<c0008900>] do_one_initcall+0x108/0x17c
[    5.512593]        [<c0483858>] kernel_init_freeable+0xec/0x1b4
[    5.518562]        [<c034f398>] kernel_init+0x8/0xe4
[    5.523562]        [<c0009448>] ret_from_fork+0x14/0x2c
[    5.528812]
-> #3 (&sb->s_type->i_mutex_key#2){+.+.+.}:
[    5.534312]        [<c004e8e8>] lock_acquire+0x64/0x78
[    5.539468]        [<c0355d5c>] mutex_lock_nested+0x5c/0x2ec
[    5.545187]        [<c017a6f8>] __create_file+0x50/0x25c
[    5.550531]        [<c017a98c>] debugfs_create_dir+0x1c/0x28
[    5.556218]        [<c026cfc4>] clk_debug_create_subtree+0x1c/0x108
[    5.562500]        [<c0495bfc>] clk_debug_init+0x68/0xc0
[    5.567875]        [<c0008900>] do_one_initcall+0x108/0x17c
[    5.573468]        [<c0483858>] kernel_init_freeable+0xec/0x1b4
[    5.579437]        [<c034f398>] kernel_init+0x8/0xe4
[    5.584437]        [<c0009448>] ret_from_fork+0x14/0x2c
[    5.589687]
-> #2 (prepare_lock){+.+.+.}:
[    5.593937]        [<c004e8e8>] lock_acquire+0x64/0x78
[    5.599125]        [<c0355d5c>] mutex_lock_nested+0x5c/0x2ec
[    5.604812]        [<c026d400>] clk_prepare+0x18/0x38
[    5.609906]        [<c023a2f8>] __gpmi_enable_clk+0x30/0xb0
[    5.615531]        [<c023a7bc>] gpmi_begin+0x18/0x530
[    5.620625]        [<c0239244>] gpmi_select_chip+0x3c/0x54
[    5.626156]        [<c02341ac>] nand_do_read_ops+0x7c/0x3e4
[    5.631750]        [<c023483c>] nand_read+0x50/0x74
[    5.636656]        [<c02198e4>] part_read+0x5c/0xa4
[    5.641593]        [<c0217404>] mtd_read+0x84/0xb8
[    5.646406]        [<c02450cc>] ubi_io_read+0xa0/0x2c0
[    5.651593]        [<c0242640>] ubi_eba_read_leb+0x190/0x424
[    5.657281]        [<c0241b18>] ubi_leb_read+0xac/0x120
[    5.662562]        [<c01503e4>] ubifs_leb_read+0x28/0x8c
[    5.667906]        [<c0151f74>] ubifs_read_node+0x98/0x2a0
[    5.673437]        [<c014e780>] ubifs_read_sb_node+0x54/0x78
[    5.679125]        [<c014f444>] ubifs_read_superblock+0xc60/0x163c
[    5.685343]        [<c014d64c>] ubifs_mount+0x800/0x171c
[    5.690687]        [<c00b5740>] mount_fs+0x44/0x184
[    5.695593]        [<c00cd7ec>] vfs_kern_mount+0x4c/0xc0
[    5.700968]        [<c00cf394>] do_mount+0x18c/0x8d0
[    5.705968]        [<c00cfb5c>] sys_mount+0x84/0xb8
[    5.710875]        [<c0483bc8>] mount_block_root+0x118/0x258
[    5.716562]        [<c0483eac>] prepare_namespace+0x8c/0x17c
[    5.722281]        [<c034f398>] kernel_init+0x8/0xe4
[    5.727281]        [<c0009448>] ret_from_fork+0x14/0x2c
[    5.732531]
-> #1 (&le->mutex){++++..}:
[    5.736625]        [<c004e8e8>] lock_acquire+0x64/0x78
[    5.741812]        [<c0356468>] down_read+0x40/0x54
[    5.746718]        [<c02424e4>] ubi_eba_read_leb+0x34/0x424
[    5.752312]        [<c0241b18>] ubi_leb_read+0xac/0x120
[    5.757562]        [<c01503e4>] ubifs_leb_read+0x28/0x8c
[    5.762937]        [<c0151f74>] ubifs_read_node+0x98/0x2a0
[    5.768437]        [<c016edc0>] ubifs_load_znode+0x88/0x560
[    5.774062]        [<c0155254>] ubifs_lookup_level0+0x190/0x1dc
[    5.780031]        [<c01552e4>] ubifs_tnc_locate+0x44/0x198
[    5.785656]        [<c014c614>] ubifs_iget+0x6c/0x8a4
[    5.790718]        [<c014da64>] ubifs_mount+0xc18/0x171c
[    5.796093]        [<c00b5740>] mount_fs+0x44/0x184
[    5.801000]        [<c00cd7ec>] vfs_kern_mount+0x4c/0xc0
[    5.806343]        [<c00cf394>] do_mount+0x18c/0x8d0
[    5.811343]        [<c00cfb5c>] sys_mount+0x84/0xb8
[    5.816250]        [<c0483bc8>] mount_block_root+0x118/0x258
[    5.821968]        [<c0483eac>] prepare_namespace+0x8c/0x17c
[    5.827656]        [<c034f398>] kernel_init+0x8/0xe4
[    5.832656]        [<c0009448>] ret_from_fork+0x14/0x2c
[    5.837906]
-> #0 (&c->tnc_mutex){+.+...}:
[    5.842250]        [<c004de48>] __lock_acquire+0x14ec/0x1b08
[    5.847968]        [<c004e8e8>] lock_acquire+0x64/0x78
[    5.853125]        [<c0355d5c>] mutex_lock_nested+0x5c/0x2ec
[    5.858812]        [<c01552d0>] ubifs_tnc_locate+0x30/0x198
[    5.864437]        [<c0155a48>] ubifs_tnc_lookup_nm+0x28/0x150
[    5.870312]        [<c016fc18>] ubifs_getxattr+0xc0/0x254
[    5.875750]        [<c018e468>] inode_doinit_with_dentry+0x25c/0x55c
[    5.882125]        [<c018f1a8>] sb_finish_set_opts+0xa4/0x21c
[    5.887906]        [<c019055c>] selinux_set_mnt_opts+0x2ec/0x4b8
[    5.893968]        [<c01907dc>] superblock_doinit+0xb4/0xc0
[    5.899562]        [<c00b51f4>] iterate_supers+0xb4/0xdc
[    5.904906]        [<c01a02e8>] security_load_policy+0x248/0x3c4
[    5.910968]        [<c0194994>] sel_write_load+0x9c/0x6a0
[    5.916406]        [<c00b2148>] vfs_write+0xa0/0x17c
[    5.921406]        [<c00b2450>] sys_write+0x3c/0x70
[    5.926343]        [<c00093a0>] ret_fast_syscall+0x0/0x38
[    5.931781]
[    5.931781] other info that might help us debug this:
[    5.931781]
[    5.939781] Chain exists of:
  &c->tnc_mutex --> &sb->s_type->i_mutex_key#2 --> &isec->lock
[    5.948500]  Possible unsafe locking scenario:
[    5.948500]
[    5.954437]        CPU0                    CPU1
[    5.958968]        ----                    ----
[    5.963500]   lock(&isec->lock);
[    5.966781]                                lock(&sb->s_type->i_mutex_key#2);
[    5.973843]                                lock(&isec->lock);
[    5.979625]   lock(&c->tnc_mutex);
[    5.983062]
[    5.983062]  *** DEADLOCK ***
[    5.983062]
[    5.989000] 4 locks held by systemd/1:
[    5.992781]  #0:  (sel_mutex){+.+.+.}, at: [<c0194918>] sel_write_load+0x20/0x6a0
[    6.000343]  #1:  (&type->s_umount_key#26){.+.+..}, at: [<c00b51d0>] iterate_supers+0x90/0xdc
[    6.008968]  #2:  (&sbsec->lock){+.+.+.}, at: [<c01902d4>] selinux_set_mnt_opts+0x64/0x4b8
[    6.017343]  #3:  (&isec->lock){+.+.+.}, at: [<c018e298>] inode_doinit_with_dentry+0x8c/0x55c
[    6.025937]
[    6.025937] stack backtrace:
[    6.030375] [<c000d0f0>] (unwind_backtrace+0x0/0xf0) from [<c0351a2c>] (print_circular_bug+0x25c/0x2a8)
[    6.039843] [<c0351a2c>] (print_circular_bug+0x25c/0x2a8) from [<c004de48>] (__lock_acquire+0x14ec/0x1b08)
[    6.049531] [<c004de48>] (__lock_acquire+0x14ec/0x1b08) from [<c004e8e8>] (lock_acquire+0x64/0x78)
[    6.058531] [<c004e8e8>] (lock_acquire+0x64/0x78) from [<c0355d5c>] (mutex_lock_nested+0x5c/0x2ec)
[    6.067531] [<c0355d5c>] (mutex_lock_nested+0x5c/0x2ec) from [<c01552d0>] (ubifs_tnc_locate+0x30/0x198)
[    6.076968] [<c01552d0>] (ubifs_tnc_locate+0x30/0x198) from [<c0155a48>] (ubifs_tnc_lookup_nm+0x28/0x150)
[    6.086593] [<c0155a48>] (ubifs_tnc_lookup_nm+0x28/0x150) from [<c016fc18>] (ubifs_getxattr+0xc0/0x254)
[    6.096031] [<c016fc18>] (ubifs_getxattr+0xc0/0x254) from [<c018e468>] (inode_doinit_with_dentry+0x25c/0x55c)
[    6.105968] [<c018e468>] (inode_doinit_with_dentry+0x25c/0x55c) from [<c018f1a8>] (sb_finish_set_opts+0xa4/0x21c)
[    6.116281] [<c018f1a8>] (sb_finish_set_opts+0xa4/0x21c) from [<c019055c>] (selinux_set_mnt_opts+0x2ec/0x4b8)
[    6.126218] [<c019055c>] (selinux_set_mnt_opts+0x2ec/0x4b8) from [<c01907dc>] (superblock_doinit+0xb4/0xc0)
[    6.136000] [<c01907dc>] (superblock_doinit+0xb4/0xc0) from [<c00b51f4>] (iterate_supers+0xb4/0xdc)
[    6.145093] [<c00b51f4>] (iterate_supers+0xb4/0xdc) from [<c01a02e8>] (security_load_policy+0x248/0x3c4)
[    6.154625] [<c01a02e8>] (security_load_policy+0x248/0x3c4) from [<c0194994>] (sel_write_load+0x9c/0x6a0)
[    6.164218] [<c0194994>] (sel_write_load+0x9c/0x6a0) from [<c00b2148>] (vfs_write+0xa0/0x17c)
[    6.172781] [<c00b2148>] (vfs_write+0xa0/0x17c) from [<c00b2450>] (sys_write+0x3c/0x70)
[    6.180843] [<c00b2450>] (sys_write+0x3c/0x70) from [<c00093a0>] (ret_fast_syscall+0x0/0x38)

Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
 include/linux/fs.h       |    1 +
 security/selinux/hooks.c |    2 ++
 2 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7617ee0..ccd49e1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1824,6 +1824,7 @@ struct file_system_type {
 	struct lock_class_key i_lock_key;
 	struct lock_class_key i_mutex_key;
 	struct lock_class_key i_mutex_dir_key;
+	struct lock_class_key i_security_lock_key;
 };
 
 extern struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ef26e96..13ccbb0 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -207,6 +207,8 @@ static int inode_alloc_security(struct inode *inode)
 		return -ENOMEM;
 
 	mutex_init(&isec->lock);
+	lockdep_set_class(&isec->lock,
+			  &inode->i_sb->s_type->i_security_lock_key);
 	INIT_LIST_HEAD(&isec->list);
 	isec->inode = inode;
 	isec->sid = SECINITSID_UNLABELED;
-- 
1.7.7.6

