ocfs2: dlmfs: fix error handling of user_dlm_destroy_lock
CVE: CVE-2022-49337
Component: kernel
Severity: None
Release date: 2022-01-01T00:00:00+00:00

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: dlmfs: fix error handling of user_dlm_destroy_lock

When user_dlm_destroy_lock failed, it didn't clean up the flags it set
before exit.  For USER_LOCK_IN_TEARDOWN, if this function fails because of
lock is still in used, next time when unlink invokes this function, it
will return succeed, and then unlink will remove inode and dentry if lock
is not in used(file closed), but the dlm lock is still linked in dlm lock
resource, then when bast come in, it will trigger a panic due to
user-after-free.  See the following panic call trace.  To fix this,
USER_LOCK_IN_TEARDOWN should be reverted if fail.  And also error should
be returned if USER_LOCK_IN_TEARDOWN is set to let user know that unlink
fail.

For the case of ocfs2_dlm_unlock failure, besides USER_LOCK_IN_TEARDOWN,
USER_LOCK_BUSY is also required to be cleared.  Even though spin lock is
released in between, but USER_LOCK_IN_TEARDOWN is still set, for
USER_LOCK_BUSY, if before every place that waits on this flag,
USER_LOCK_IN_TEARDOWN is checked to bail out, that will make sure no flow
waits on the busy flag set by user_dlm_destroy_lock(), then we can
simplely revert USER_LOCK_BUSY when ocfs2_dlm_unlock fails.  Fix
user_dlm_cluster_lock() which is the only function not following this.

[  941.336392] (python,26174,16):dlmfs_unlink:562 ERROR: unlink
004fb0000060000b5a90b8c847b72e1, error -16 from destroy
[  989.757536] ------------[ cut here ]------------
[  989.757709] kernel BUG at fs/ocfs2/dlmfs/userdlm.c:173!
[  989.757876] invalid opcode: 0000 [#1] SMP
[  989.758027] Modules linked in: ksplice_2zhuk2jr_ib_ipoib_new(O)
ksplice_2zhuk2jr(O) mptctl mptbase xen_netback xen_blkback xen_gntalloc
xen_gntdev xen_evtchn cdc_ether usbnet mii ocfs2 jbd2 rpcsec_gss_krb5
auth_rpcgss nfsv4 nfsv3 nfs_acl nfs fscache lockd grace ocfs2_dlmfs
ocfs2_stack_o2cb ocfs2_dlm ocfs2_nodemanager ocfs2_stackglue configfs bnx2fc
fcoe libfcoe libfc scsi_transport_fc sunrpc ipmi_devintf bridge stp llc
rds_rdma rds bonding ib_sdp ib_ipoib rdma_ucm ib_ucm ib_uverbs ib_umad
rdma_cm ib_cm iw_cm falcon_lsm_serviceable(PE) falcon_nf_netcontain(PE)
mlx4_vnic falcon_kal(E) falcon_lsm_pinned_13402(E) mlx4_ib ib_sa ib_mad
ib_core ib_addr xenfs xen_privcmd dm_multipath iTCO_wdt iTCO_vendor_support
pcspkr sb_edac edac_core i2c_i801 lpc_ich mfd_core ipmi_ssif i2c_core ipmi_si
ipmi_msghandler
[  989.760686]  ioatdma sg ext3 jbd mbcache sd_mod ahci libahci ixgbe dca ptp
pps_core vxlan udp_tunnel ip6_udp_tunnel megaraid_sas mlx4_core crc32c_intel
be2iscsi bnx2i cnic uio cxgb4i cxgb4 cxgb3i libcxgbi ipv6 cxgb3 mdio
libiscsi_tcp qla4xxx iscsi_boot_sysfs libiscsi scsi_transport_iscsi wmi
dm_mirror dm_region_hash dm_log dm_mod [last unloaded:
ksplice_2zhuk2jr_ib_ipoib_old]
[  989.761987] CPU: 10 PID: 19102 Comm: dlm_thread Tainted: P           OE
4.1.12-124.57.1.el6uek.x86_64 #2
[  989.762290] Hardware name: Oracle Corporation ORACLE SERVER
X5-2/ASM,MOTHERBOARD,1U, BIOS 30350100 06/17/2021
[  989.762599] task: ffff880178af6200 ti: ffff88017f7c8000 task.ti:
ffff88017f7c8000
[  989.762848] RIP: e030:[<ffffffffc07d4316>]  [<ffffffffc07d4316>]
__user_dlm_queue_lockres.part.4+0x76/0x80 [ocfs2_dlmfs]
[  989.763185] RSP: e02b:ffff88017f7cbcb8  EFLAGS: 00010246
[  989.763353] RAX: 0000000000000000 RBX: ffff880174d48008 RCX:
0000000000000003
[  989.763565] RDX: 0000000000120012 RSI: 0000000000000003 RDI:
ffff880174d48170
[  989.763778] RBP: ffff88017f7cbcc8 R08: ffff88021f4293b0 R09:
0000000000000000
[  989.763991] R10: ffff880179c8c000 R11: 0000000000000003 R12:
ffff880174d48008
[  989.764204] R13: 0000000000000003 R14: ffff880179c8c000 R15:
ffff88021db7a000
[  989.764422] FS:  0000000000000000(0000) GS:ffff880247480000(0000)
knlGS:ffff880247480000
[  989.764685] CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
[  989.764865] CR2: ffff8000007f6800 CR3: 0000000001ae0000 CR4:
0000000000042660
[  989.765081] Stack:
[  989.765167]  00000000000
---truncated---


Remediation: