SELinux + ubifs: possible circular locking dependency

[Marc Kleine-Budde <mkl@pengutronix.de>]

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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:

This warning shows up every boot, but not again later. Is lockep
automatically disabled after the first circular lockdep warning?

This particular situation, where the dependency chain is occurs as far
as I understand only at boot. Three functions in this chain are only
called once:
- pinctrl_init()
- clk_debug_init()
- mount_block_root()

Another critical ingredient is security_load_policy().

Is this really an uncritical catch of the lock validator? If so, is it
possible to annotate this, so that the system boot up quietly?

> [    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)

regards,
Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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