| Message ID | 20200510051347.1906-1-cai@lca.pw (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc/powernv/pci: fix a RCU-list lock | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (1bc92fe3175eb26ff37e580c0383d7a9abe06835) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | warning | total: 0 errors, 1 warnings, 0 checks, 16 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
On Sun, 10 May 2020 01:13:47 -0400, Qian Cai wrote: > 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!! > > [...] Applied to powerpc/next. [1/1] powerpc/powernv/pci: fix a RCU-list lock https://git.kernel.org/powerpc/c/c9790fb5df461c91d3fff1d864c1acb8baf5ad5c cheers
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;
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(+)