Re: SELinux + ubifs: possible circular locking dependency

Artem Bityutskiy
2013-02-13T12:47:44Z

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On Fri, 2013-02-08 at 15:10 +0100, Marc Kleine-Budde wrote:
> Hello,
>
> I'm on a arm imx28 v3.8-rc6 (+ a handfull of patches to support the
> custom board) but no modifications on ubifs, selinux or the vfs layer.
> And not including the xattr patches by Subodh Nijsure.
>
> When booting with SELinux and lockdep enabled I see this _possible_
> circular locking dependency:

I guess one needs to really understand how lockdep works, because it
seems there is no direct 'tnc_mutex -> isec->lock', and lockdep somehow
deducts this connection inderectly.

However, it seems I see what _may_ be the reason, and here is a patch
which I think may fix the issue. Would you please test/review it? It is
inlined and also attached.

>From a2b29a190227959bdeadf8d412745003c86857ef Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Date: Wed, 13 Feb 2013 13:49:14 +0200
Subject: [PATCH] selinux: do not confuse lockdep

Selinux initializes all per-inode 'isec->lock' mutexes in one single place,
which makes lockdep believe they all belong to the same class, which will make
lockdep treat all 'isec->lock' mutexes equivalent. This leads to a lockdep
false-positive reported by Marc Kleine-Budde <mkl@pengutronix.de> (see at the
end).

Frankly, I failed to understand the warning and this fix is more of a guess of
what would be the root-cause. I would appreciate if someone could explain me
what this warning actually tells, because I cannot see any 'c->tnc_mutex ->
isec->lock' chain in the code! Where this chain comes from:

"&c->tnc_mutex --> &sb->s_type->i_mutex_key#2 --> &isec->lock"

The lockdep complaint:

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)

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
security/selinux/hooks.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ef26e96..328180e 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -207,6 +207,7 @@ 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_mutex_key);
INIT_LIST_HEAD(&isec->list);
isec->inode = inode;
isec->sid = SECINITSID_UNLABELED;
--
1.7.10.4

--
Best Regards,
Artem Bityutskiy

[-- Attachment #2: 0001-selinux-do-not-confuse-lockdep.patch --]
[-- Type: text/x-patch, Size: 10521 bytes --]

>From a2b29a190227959bdeadf8d412745003c86857ef Mon Sep 17 00:00:00 2001
From: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Date: Wed, 13 Feb 2013 13:49:14 +0200
Subject: [PATCH] selinux: do not confuse lockdep

Selinux initializes all per-inode 'isec->lock' mutexes in one single place,
which makes lockdep believe they all belong to the same class, which will make
lockdep treat all 'isec->lock' mutexes equivalent. This leads to a lockdep
false-positive reported by Marc Kleine-Budde <mkl@pengutronix.de> (see at the
end).

Frankly, I failed to understand the warning and this fix is more of a guess of
what would be the root-cause. I would appreciate if someone could explain me
what this warning actually tells, because I cannot see any 'c->tnc_mutex ->
isec->lock' chain in the code! Where this chain comes from:

"&c->tnc_mutex --> &sb->s_type->i_mutex_key#2 --> &isec->lock"

The lockdep complaint:

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)

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
---
security/selinux/hooks.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ef26e96..328180e 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -207,6 +207,7 @@ 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_mutex_key);
INIT_LIST_HEAD(&isec->list);
isec->inode = inode;
isec->sid = SECINITSID_UNLABELED;
--
1.7.10.4