lkml.org 
[lkml]   [2020]   [May]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] powerpc/powernv/pci: fix a RCU-list lock
Date
It is unsafe to traverse tbl->it_group_list without the RCU read lock.

WARNING: suspicious RCU usage
5.7.0-rc4-next-20200508 #1 Not tainted
-----------------------------
arch/powerpc/platforms/powernv/pci-ioda-tce.c:355 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
3 locks held by qemu-kvm/4305:
#0: c000000bc3fe6988 (&container->group_lock){++++}-{3:3}, at: vfio_fops_unl_ioctl+0x108/0x410 [vfio]
#1: c00800000fcc7400 (&vfio.iommu_drivers_lock){+.+.}-{3:3}, at: vfio_fops_unl_ioctl+0x148/0x410 [vfio]
#2: c000000bc3fe4d68 (&container->lock){+.+.}-{3:3}, at: tce_iommu_attach_group+0x3c/0x4f0 [vfio_iommu_spapr_tce]

stack backtrace:
CPU: 4 PID: 4305 Comm: qemu-kvm Not tainted 5.7.0-rc4-next-20200508 #1
Call Trace:
[c0000010f29afa60] [c0000000007154c8] dump_stack+0xfc/0x174 (unreliable)
[c0000010f29afab0] [c0000000001d8ff0] lockdep_rcu_suspicious+0x140/0x164
[c0000010f29afb30] [c0000000000dae2c] pnv_pci_unlink_table_and_group+0x11c/0x200
[c0000010f29afb70] [c0000000000d4a34] pnv_pci_ioda2_unset_window+0xc4/0x190
[c0000010f29afbf0] [c0000000000d4b4c] pnv_ioda2_take_ownership+0x4c/0xd0
[c0000010f29afc30] [c00800000fd60ee0] tce_iommu_attach_group+0x2c8/0x4f0 [vfio_iommu_spapr_tce]
[c0000010f29afcd0] [c00800000fcc11a0] vfio_fops_unl_ioctl+0x238/0x410 [vfio]
[c0000010f29afd50] [c0000000005430a8] ksys_ioctl+0xd8/0x130
[c0000010f29afda0] [c000000000543128] sys_ioctl+0x28/0x40
[c0000010f29afdc0] [c000000000038af4] system_call_exception+0x114/0x1e0
[c0000010f29afe20] [c00000000000c8f0] system_call_common+0xf0/0x278

Signed-off-by: Qian Cai <cai@lca.pw>
---
arch/powerpc/platforms/powernv/pci-ioda-tce.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/platforms/powernv/pci-ioda-tce.c b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
index 5dc6847d5f4c..6be9cf292b4e 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda-tce.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda-tce.c
@@ -352,6 +352,8 @@ void pnv_pci_unlink_table_and_group(struct iommu_table *tbl,

/* Remove link to a group from table's list of attached groups */
found = false;
+
+ rcu_read_lock();
list_for_each_entry_rcu(tgl, &tbl->it_group_list, next) {
if (tgl->table_group == table_group) {
list_del_rcu(&tgl->next);
@@ -360,6 +362,8 @@ void pnv_pci_unlink_table_and_group(struct iommu_table *tbl,
break;
}
}
+ rcu_read_unlock();
+
if (WARN_ON(!found))
return;

--
2.21.0 (Apple Git-122.2)
\
 
 \ /
  Last update: 2020-05-10 07:15    [W:0.139 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site