[Cluster-devel] [PATCHv2 dlm/next 0/2] fs: dlm: some callback and lowcomm fixes

[Cluster-devel] [PATCHv2 dlm/next 0/2] fs: dlm: some callback and lowcomm fixes

[Alexander Aring]

Hi,

I currently look a little bit deeper into the callback handling of dlm.
I have some local branches which does more some rework and moving away
from the lkb_callbacks[] array per lkb and using a queue for handling
callbacks. However those are issues which I currently found for now
and should be fixed.

- Alex

changes since v2:

 - drop patches 2/3 and 3/3 as it looks okay. Sorry about the noise.
 - change commit messages regarding v2 changes.
 - add patch "fs: dlm: fix race in lowcomms"

Alexander Aring (2):
  fs: dlm: fix race in lowcomms
  fs: dlm: fix race between test_bit() and queue_work()

 fs/dlm/ast.c      | 6 ++++--
 fs/dlm/lowcomms.c | 4 ++++
 2 files changed, 8 insertions(+), 2 deletions(-)

-- 
2.31.1

[Cluster-devel] [PATCHv2 dlm/next 1/2] fs: dlm: fix race in lowcomms

[Alexander Aring]

This patch fixes a race between queue_work() in
_dlm_lowcomms_commit_msg() and srcu_read_unlock(). The queue_work() can
take the final reference of a dlm_msg and so msg->idx can contain
garbage which is signaled by the following warning:

[  676.237050] ------------[ cut here ]------------
[  676.237052] WARNING: CPU: 0 PID: 1060 at include/linux/srcu.h:189 dlm_lowcomms_commit_msg+0x41/0x50
[  676.238945] Modules linked in: dlm_locktorture torture rpcsec_gss_krb5 intel_rapl_msr intel_rapl_common iTCO_wdt iTCO_vendor_support qxl kvm_intel drm_ttm_helper vmw_vsock_virtio_transport kvm vmw_vsock_virtio_transport_common ttm irqbypass crc32_pclmul joydev crc32c_intel serio_raw drm_kms_helper vsock virtio_scsi virtio_console virtio_balloon snd_pcm drm syscopyarea sysfillrect sysimgblt snd_timer fb_sys_fops i2c_i801 lpc_ich snd i2c_smbus soundcore pcspkr
[  676.244227] CPU: 0 PID: 1060 Comm: lock_torture_wr Not tainted 5.19.0-rc3+ #1546
[  676.245216] Hardware name: Red Hat KVM/RHEL-AV, BIOS 1.16.0-2.module+el8.7.0+15506+033991b0 04/01/2014
[  676.246460] RIP: 0010:dlm_lowcomms_commit_msg+0x41/0x50
[  676.247132] Code: fe ff ff ff 75 24 48 c7 c6 bd 0f 49 bb 48 c7 c7 38 7c 01 bd e8 00 e7 ca ff 89 de 48 c7 c7 60 78 01 bd e8 42 3d cd ff 5b 5d c3 <0f> 0b eb d8 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48
[  676.249253] RSP: 0018:ffffa401c18ffc68 EFLAGS: 00010282
[  676.249855] RAX: 0000000000000001 RBX: 00000000ffff8b76 RCX: 0000000000000006
[  676.250713] RDX: 0000000000000000 RSI: ffffffffbccf3a10 RDI: ffffffffbcc7b62e
[  676.251610] RBP: ffffa401c18ffc70 R08: 0000000000000001 R09: 0000000000000001
[  676.252481] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000005
[  676.253421] R13: ffff8b76786ec370 R14: ffff8b76786ec370 R15: ffff8b76786ec480
[  676.254257] FS:  0000000000000000(0000) GS:ffff8b7777800000(0000) knlGS:0000000000000000
[  676.255239] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  676.255897] CR2: 00005590205d88b8 CR3: 000000017656c003 CR4: 0000000000770ee0
[  676.256734] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  676.257567] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  676.258397] PKRU: 55555554
[  676.258729] Call Trace:
[  676.259063]  <TASK>
[  676.259354]  dlm_midcomms_commit_mhandle+0xcc/0x110
[  676.259964]  queue_bast+0x8b/0xb0
[  676.260423]  grant_pending_locks+0x166/0x1b0
[  676.261007]  _unlock_lock+0x75/0x90
[  676.261469]  unlock_lock.isra.57+0x62/0xa0
[  676.262009]  dlm_unlock+0x21e/0x330
[  676.262457]  ? lock_torture_stats+0x80/0x80 [dlm_locktorture]
[  676.263183]  torture_unlock+0x5a/0x90 [dlm_locktorture]
[  676.263815]  ? preempt_count_sub+0xba/0x100
[  676.264361]  ? complete+0x1d/0x60
[  676.264777]  lock_torture_writer+0xb8/0x150 [dlm_locktorture]
[  676.265555]  kthread+0x10a/0x130
[  676.266007]  ? kthread_complete_and_exit+0x20/0x20
[  676.266616]  ret_from_fork+0x22/0x30
[  676.267097]  </TASK>
[  676.267381] irq event stamp: 9579855
[  676.267824] hardirqs last  enabled at (9579863): [<ffffffffbb14e6f8>] __up_console_sem+0x58/0x60
[  676.268896] hardirqs last disabled at (9579872): [<ffffffffbb14e6dd>] __up_console_sem+0x3d/0x60
[  676.270008] softirqs last  enabled at (9579798): [<ffffffffbc200349>] __do_softirq+0x349/0x4c7
[  676.271438] softirqs last disabled at (9579897): [<ffffffffbb0d54c0>] irq_exit_rcu+0xb0/0xf0
[  676.272796] ---[ end trace 0000000000000000 ]---

I reproduced this warning with dlm_locktorture test which is currently
not upstream. However this patch fix the issue by make a additional
refcount between dlm_lowcomms_new_msg() and dlm_lowcomms_commit_msg().
In case of the race the kref_put() in dlm_lowcomms_commit_msg() will be
the final put.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/lowcomms.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index a4e84e8d94c8..59f64c596233 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1336,6 +1336,8 @@ struct dlm_msg *dlm_lowcomms_new_msg(int nodeid, int len, gfp_t allocation,
 		return NULL;
 	}
 
+	/* for dlm_lowcomms_commit_msg() */
+	kref_get(&msg->ref);
 	/* we assume if successful commit must called */
 	msg->idx = idx;
 	return msg;
@@ -1375,6 +1377,8 @@ void dlm_lowcomms_commit_msg(struct dlm_msg *msg)
 {
 	_dlm_lowcomms_commit_msg(msg);
 	srcu_read_unlock(&connections_srcu, msg->idx);
+	/* because dlm_lowcomms_new_msg() */
+	kref_put(&msg->ref, dlm_msg_release);
 }
 #endif
 
-- 
2.31.1

[Cluster-devel] [PATCHv2 dlm/next 1/2] fs: dlm: fix race in lowcomms

[Alexander Aring]

Hi,

On Mon, Jul 25, 2022 at 3:53 PM Alexander Aring <aahringo@redhat.com> wrote:
>
> This patch fixes a race between queue_work() in
> _dlm_lowcomms_commit_msg() and srcu_read_unlock(). The queue_work() can
> take the final reference of a dlm_msg and so msg->idx can contain
> garbage which is signaled by the following warning:
>
> [  676.237050] ------------[ cut here ]------------
> [  676.237052] WARNING: CPU: 0 PID: 1060 at include/linux/srcu.h:189 dlm_lowcomms_commit_msg+0x41/0x50
> [  676.238945] Modules linked in: dlm_locktorture torture rpcsec_gss_krb5 intel_rapl_msr intel_rapl_common iTCO_wdt iTCO_vendor_support qxl kvm_intel drm_ttm_helper vmw_vsock_virtio_transport kvm vmw_vsock_virtio_transport_common ttm irqbypass crc32_pclmul joydev crc32c_intel serio_raw drm_kms_helper vsock virtio_scsi virtio_console virtio_balloon snd_pcm drm syscopyarea sysfillrect sysimgblt snd_timer fb_sys_fops i2c_i801 lpc_ich snd i2c_smbus soundcore pcspkr
> [  676.244227] CPU: 0 PID: 1060 Comm: lock_torture_wr Not tainted 5.19.0-rc3+ #1546
> [  676.245216] Hardware name: Red Hat KVM/RHEL-AV, BIOS 1.16.0-2.module+el8.7.0+15506+033991b0 04/01/2014
> [  676.246460] RIP: 0010:dlm_lowcomms_commit_msg+0x41/0x50
> [  676.247132] Code: fe ff ff ff 75 24 48 c7 c6 bd 0f 49 bb 48 c7 c7 38 7c 01 bd e8 00 e7 ca ff 89 de 48 c7 c7 60 78 01 bd e8 42 3d cd ff 5b 5d c3 <0f> 0b eb d8 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48
> [  676.249253] RSP: 0018:ffffa401c18ffc68 EFLAGS: 00010282
> [  676.249855] RAX: 0000000000000001 RBX: 00000000ffff8b76 RCX: 0000000000000006
> [  676.250713] RDX: 0000000000000000 RSI: ffffffffbccf3a10 RDI: ffffffffbcc7b62e
> [  676.251610] RBP: ffffa401c18ffc70 R08: 0000000000000001 R09: 0000000000000001
> [  676.252481] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000005
> [  676.253421] R13: ffff8b76786ec370 R14: ffff8b76786ec370 R15: ffff8b76786ec480
> [  676.254257] FS:  0000000000000000(0000) GS:ffff8b7777800000(0000) knlGS:0000000000000000
> [  676.255239] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  676.255897] CR2: 00005590205d88b8 CR3: 000000017656c003 CR4: 0000000000770ee0
> [  676.256734] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  676.257567] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  676.258397] PKRU: 55555554
> [  676.258729] Call Trace:
> [  676.259063]  <TASK>
> [  676.259354]  dlm_midcomms_commit_mhandle+0xcc/0x110
> [  676.259964]  queue_bast+0x8b/0xb0
> [  676.260423]  grant_pending_locks+0x166/0x1b0
> [  676.261007]  _unlock_lock+0x75/0x90
> [  676.261469]  unlock_lock.isra.57+0x62/0xa0
> [  676.262009]  dlm_unlock+0x21e/0x330
> [  676.262457]  ? lock_torture_stats+0x80/0x80 [dlm_locktorture]
> [  676.263183]  torture_unlock+0x5a/0x90 [dlm_locktorture]
> [  676.263815]  ? preempt_count_sub+0xba/0x100
> [  676.264361]  ? complete+0x1d/0x60
> [  676.264777]  lock_torture_writer+0xb8/0x150 [dlm_locktorture]
> [  676.265555]  kthread+0x10a/0x130
> [  676.266007]  ? kthread_complete_and_exit+0x20/0x20
> [  676.266616]  ret_from_fork+0x22/0x30
> [  676.267097]  </TASK>
> [  676.267381] irq event stamp: 9579855
> [  676.267824] hardirqs last  enabled at (9579863): [<ffffffffbb14e6f8>] __up_console_sem+0x58/0x60
> [  676.268896] hardirqs last disabled at (9579872): [<ffffffffbb14e6dd>] __up_console_sem+0x3d/0x60
> [  676.270008] softirqs last  enabled at (9579798): [<ffffffffbc200349>] __do_softirq+0x349/0x4c7
> [  676.271438] softirqs last disabled at (9579897): [<ffffffffbb0d54c0>] irq_exit_rcu+0xb0/0xf0
> [  676.272796] ---[ end trace 0000000000000000 ]---
>
> I reproduced this warning with dlm_locktorture test which is currently
> not upstream. However this patch fix the issue by make a additional
> refcount between dlm_lowcomms_new_msg() and dlm_lowcomms_commit_msg().
> In case of the race the kref_put() in dlm_lowcomms_commit_msg() will be
> the final put.
>
> Signed-off-by: Alexander Aring <aahringo@redhat.com>

grml, now I forgot in this patch Cc: stable and fixes-tag. Will send v3. Sorry.

- Alex

[Cluster-devel] [PATCHv2 dlm/next 2/2] fs: dlm: fix race between test_bit() and queue_work()

[Alexander Aring]

This patch will fix a race by surround ls_cb_mutex in set_bit() and the
test_bit() and it's conditional code blocks for LSFL_CB_DELAY.

The function dlm_callback_stop() has the idea to stop all callbacks and
flush all currently queued onces. The set_bit() is not enough because
there can be still queue_work() around after the workqueue was flushed.
To avoid queue_work() after set_bit() we surround both by ls_cb_mutex
lock.

Cc: stable at vger.kernel.org
Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 fs/dlm/ast.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/dlm/ast.c b/fs/dlm/ast.c
index 19ef136f9e4f..a44cc42b6317 100644
--- a/fs/dlm/ast.c
+++ b/fs/dlm/ast.c
@@ -200,13 +200,13 @@ void dlm_add_cb(struct dlm_lkb *lkb, uint32_t flags, int mode, int status,
 	if (!prev_seq) {
 		kref_get(&lkb->lkb_ref);
 
+		mutex_lock(&ls->ls_cb_mutex);
 		if (test_bit(LSFL_CB_DELAY, &ls->ls_flags)) {
-			mutex_lock(&ls->ls_cb_mutex);
 			list_add(&lkb->lkb_cb_list, &ls->ls_cb_delay);
-			mutex_unlock(&ls->ls_cb_mutex);
 		} else {
 			queue_work(ls->ls_callback_wq, &lkb->lkb_cb_work);
 		}
+		mutex_unlock(&ls->ls_cb_mutex);
 	}
  out:
 	mutex_unlock(&lkb->lkb_cb_mutex);
@@ -288,7 +288,9 @@ void dlm_callback_stop(struct dlm_ls *ls)
 
 void dlm_callback_suspend(struct dlm_ls *ls)
 {
+	mutex_lock(&ls->ls_cb_mutex);
 	set_bit(LSFL_CB_DELAY, &ls->ls_flags);
+	mutex_unlock(&ls->ls_cb_mutex);
 
 	if (ls->ls_callback_wq)
 		flush_workqueue(ls->ls_callback_wq);
-- 
2.31.1