Hi, On Mon, Jul 25, 2022 at 3:53 PM Alexander Aring <aahringo@xxxxxxxxxx> 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@xxxxxxxxxx> grml, now I forgot in this patch Cc: stable and fixes-tag. Will send v3. Sorry. - Alex
