From: Alex Williamson alex.williamson@redhat.com
[ Upstream commit f6944d4a0b87c16bc34ae589169e1ded3d4db08e ]
Lockdep reports the below circular locking dependency issue. The mmap_lock acquisition while holding pci_bus_sem is due to the use of copy_to_user() from within a pci_walk_bus() callback.
Building the devices array directly into the user buffer is only for convenience. Instead we can allocate a local buffer for the array, bounded by the number of devices on the bus/slot, fill the device information into this local buffer, then copy it into the user buffer outside the bus walk callback.
====================================================== WARNING: possible circular locking dependency detected 6.9.0-rc5+ #39 Not tainted ------------------------------------------------------ CPU 0/KVM/4113 is trying to acquire lock: ffff99a609ee18a8 (&vdev->vma_lock){+.+.}-{4:4}, at: vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core]
but task is already holding lock: ffff99a243a052a0 (&mm->mmap_lock){++++}-{4:4}, at: vaddr_get_pfns+0x3f/0x170 [vfio_iommu_type1]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (&mm->mmap_lock){++++}-{4:4}: __lock_acquire+0x4e4/0xb90 lock_acquire+0xbc/0x2d0 __might_fault+0x5c/0x80 _copy_to_user+0x1e/0x60 vfio_pci_fill_devs+0x9f/0x130 [vfio_pci_core] vfio_pci_walk_wrapper+0x45/0x60 [vfio_pci_core] __pci_walk_bus+0x6b/0xb0 vfio_pci_ioctl_get_pci_hot_reset_info+0x10b/0x1d0 [vfio_pci_core] vfio_pci_core_ioctl+0x1cb/0x400 [vfio_pci_core] vfio_device_fops_unl_ioctl+0x7e/0x140 [vfio] __x64_sys_ioctl+0x8a/0xc0 do_syscall_64+0x8d/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #2 (pci_bus_sem){++++}-{4:4}: __lock_acquire+0x4e4/0xb90 lock_acquire+0xbc/0x2d0 down_read+0x3e/0x160 pci_bridge_wait_for_secondary_bus.part.0+0x33/0x2d0 pci_reset_bus+0xdd/0x160 vfio_pci_dev_set_hot_reset+0x256/0x270 [vfio_pci_core] vfio_pci_ioctl_pci_hot_reset_groups+0x1a3/0x280 [vfio_pci_core] vfio_pci_core_ioctl+0x3b5/0x400 [vfio_pci_core] vfio_device_fops_unl_ioctl+0x7e/0x140 [vfio] __x64_sys_ioctl+0x8a/0xc0 do_syscall_64+0x8d/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #1 (&vdev->memory_lock){+.+.}-{4:4}: __lock_acquire+0x4e4/0xb90 lock_acquire+0xbc/0x2d0 down_write+0x3b/0xc0 vfio_pci_zap_and_down_write_memory_lock+0x1c/0x30 [vfio_pci_core] vfio_basic_config_write+0x281/0x340 [vfio_pci_core] vfio_config_do_rw+0x1fa/0x300 [vfio_pci_core] vfio_pci_config_rw+0x75/0xe50 [vfio_pci_core] vfio_pci_rw+0xea/0x1a0 [vfio_pci_core] vfs_write+0xea/0x520 __x64_sys_pwrite64+0x90/0xc0 do_syscall_64+0x8d/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e
-> #0 (&vdev->vma_lock){+.+.}-{4:4}: check_prev_add+0xeb/0xcc0 validate_chain+0x465/0x530 __lock_acquire+0x4e4/0xb90 lock_acquire+0xbc/0x2d0 __mutex_lock+0x97/0xde0 vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core] __do_fault+0x31/0x160 do_pte_missing+0x65/0x3b0 __handle_mm_fault+0x303/0x720 handle_mm_fault+0x10f/0x460 fixup_user_fault+0x7f/0x1f0 follow_fault_pfn+0x66/0x1c0 [vfio_iommu_type1] vaddr_get_pfns+0xf2/0x170 [vfio_iommu_type1] vfio_pin_pages_remote+0x348/0x4e0 [vfio_iommu_type1] vfio_pin_map_dma+0xd2/0x330 [vfio_iommu_type1] vfio_dma_do_map+0x2c0/0x440 [vfio_iommu_type1] vfio_iommu_type1_ioctl+0xc5/0x1d0 [vfio_iommu_type1] __x64_sys_ioctl+0x8a/0xc0 do_syscall_64+0x8d/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e
other info that might help us debug this:
Chain exists of: &vdev->vma_lock --> pci_bus_sem --> &mm->mmap_lock
Possible unsafe locking scenario:
block dm-0: the capability attribute has been deprecated. CPU0 CPU1 ---- ---- rlock(&mm->mmap_lock); lock(pci_bus_sem); lock(&mm->mmap_lock); lock(&vdev->vma_lock);
*** DEADLOCK ***
2 locks held by CPU 0/KVM/4113: #0: ffff99a25f294888 (&iommu->lock#2){+.+.}-{4:4}, at: vfio_dma_do_map+0x60/0x440 [vfio_iommu_type1] #1: ffff99a243a052a0 (&mm->mmap_lock){++++}-{4:4}, at: vaddr_get_pfns+0x3f/0x170 [vfio_iommu_type1]
stack backtrace: CPU: 1 PID: 4113 Comm: CPU 0/KVM Not tainted 6.9.0-rc5+ #39 Hardware name: Dell Inc. PowerEdge T640/04WYPY, BIOS 2.15.1 06/16/2022 Call Trace: <TASK> dump_stack_lvl+0x64/0xa0 check_noncircular+0x131/0x150 check_prev_add+0xeb/0xcc0 ? add_chain_cache+0x10a/0x2f0 ? __lock_acquire+0x4e4/0xb90 validate_chain+0x465/0x530 __lock_acquire+0x4e4/0xb90 lock_acquire+0xbc/0x2d0 ? vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core] ? lock_is_held_type+0x9a/0x110 __mutex_lock+0x97/0xde0 ? vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core] ? lock_acquire+0xbc/0x2d0 ? vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core] ? find_held_lock+0x2b/0x80 ? vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core] vfio_pci_mmap_fault+0x35/0x1a0 [vfio_pci_core] __do_fault+0x31/0x160 do_pte_missing+0x65/0x3b0 __handle_mm_fault+0x303/0x720 handle_mm_fault+0x10f/0x460 fixup_user_fault+0x7f/0x1f0 follow_fault_pfn+0x66/0x1c0 [vfio_iommu_type1] vaddr_get_pfns+0xf2/0x170 [vfio_iommu_type1] vfio_pin_pages_remote+0x348/0x4e0 [vfio_iommu_type1] vfio_pin_map_dma+0xd2/0x330 [vfio_iommu_type1] vfio_dma_do_map+0x2c0/0x440 [vfio_iommu_type1] vfio_iommu_type1_ioctl+0xc5/0x1d0 [vfio_iommu_type1] __x64_sys_ioctl+0x8a/0xc0 do_syscall_64+0x8d/0x170 ? rcu_core+0x8d/0x250 ? __lock_release+0x5e/0x160 ? rcu_core+0x8d/0x250 ? lock_release+0x5f/0x120 ? sched_clock+0xc/0x30 ? sched_clock_cpu+0xb/0x190 ? irqtime_account_irq+0x40/0xc0 ? __local_bh_enable+0x54/0x60 ? __do_softirq+0x315/0x3ca ? lockdep_hardirqs_on_prepare.part.0+0x97/0x140 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f8300d0357b Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 75 68 0f 00 f7 d8 64 89 01 48 RSP: 002b:00007f82ef3fb948 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f8300d0357b RDX: 00007f82ef3fb990 RSI: 0000000000003b71 RDI: 0000000000000023 RBP: 00007f82ef3fb9c0 R08: 0000000000000000 R09: 0000561b7e0bcac2 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 0000000200000000 R14: 0000381800000000 R15: 0000000000000000 </TASK>
Reviewed-by: Jason Gunthorpe jgg@nvidia.com Link: https://lore.kernel.org/r/20240503143138.3562116-1-alex.williamson@redhat.co... Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/pci/vfio_pci_core.c | 78 ++++++++++++++++++++------------ 1 file changed, 49 insertions(+), 29 deletions(-)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 1929103ee59a3..a3c545dd174ee 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -778,25 +778,26 @@ static int vfio_pci_count_devs(struct pci_dev *pdev, void *data) }
struct vfio_pci_fill_info { - struct vfio_pci_dependent_device __user *devices; - struct vfio_pci_dependent_device __user *devices_end; struct vfio_device *vdev; + struct vfio_pci_dependent_device *devices; + int nr_devices; u32 count; u32 flags; };
static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data) { - struct vfio_pci_dependent_device info = { - .segment = pci_domain_nr(pdev->bus), - .bus = pdev->bus->number, - .devfn = pdev->devfn, - }; + struct vfio_pci_dependent_device *info; struct vfio_pci_fill_info *fill = data;
- fill->count++; - if (fill->devices >= fill->devices_end) - return 0; + /* The topology changed since we counted devices */ + if (fill->count >= fill->nr_devices) + return -EAGAIN; + + info = &fill->devices[fill->count++]; + info->segment = pci_domain_nr(pdev->bus); + info->bus = pdev->bus->number; + info->devfn = pdev->devfn;
if (fill->flags & VFIO_PCI_HOT_RESET_FLAG_DEV_ID) { struct iommufd_ctx *iommufd = vfio_iommufd_device_ictx(fill->vdev); @@ -809,19 +810,19 @@ static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data) */ vdev = vfio_find_device_in_devset(dev_set, &pdev->dev); if (!vdev) { - info.devid = VFIO_PCI_DEVID_NOT_OWNED; + info->devid = VFIO_PCI_DEVID_NOT_OWNED; } else { int id = vfio_iommufd_get_dev_id(vdev, iommufd);
if (id > 0) - info.devid = id; + info->devid = id; else if (id == -ENOENT) - info.devid = VFIO_PCI_DEVID_OWNED; + info->devid = VFIO_PCI_DEVID_OWNED; else - info.devid = VFIO_PCI_DEVID_NOT_OWNED; + info->devid = VFIO_PCI_DEVID_NOT_OWNED; } /* If devid is VFIO_PCI_DEVID_NOT_OWNED, clear owned flag. */ - if (info.devid == VFIO_PCI_DEVID_NOT_OWNED) + if (info->devid == VFIO_PCI_DEVID_NOT_OWNED) fill->flags &= ~VFIO_PCI_HOT_RESET_FLAG_DEV_ID_OWNED; } else { struct iommu_group *iommu_group; @@ -830,13 +831,10 @@ static int vfio_pci_fill_devs(struct pci_dev *pdev, void *data) if (!iommu_group) return -EPERM; /* Cannot reset non-isolated devices */
- info.group_id = iommu_group_id(iommu_group); + info->group_id = iommu_group_id(iommu_group); iommu_group_put(iommu_group); }
- if (copy_to_user(fill->devices, &info, sizeof(info))) - return -EFAULT; - fill->devices++; return 0; }
@@ -1258,10 +1256,11 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info( { unsigned long minsz = offsetofend(struct vfio_pci_hot_reset_info, count); + struct vfio_pci_dependent_device *devices = NULL; struct vfio_pci_hot_reset_info hdr; struct vfio_pci_fill_info fill = {}; bool slot = false; - int ret = 0; + int ret, count;
if (copy_from_user(&hdr, arg, minsz)) return -EFAULT; @@ -1277,9 +1276,23 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info( else if (pci_probe_reset_bus(vdev->pdev->bus)) return -ENODEV;
- fill.devices = arg->devices; - fill.devices_end = arg->devices + - (hdr.argsz - sizeof(hdr)) / sizeof(arg->devices[0]); + ret = vfio_pci_for_each_slot_or_bus(vdev->pdev, vfio_pci_count_devs, + &count, slot); + if (ret) + return ret; + + if (count > (hdr.argsz - sizeof(hdr)) / sizeof(*devices)) { + hdr.count = count; + ret = -ENOSPC; + goto header; + } + + devices = kcalloc(count, sizeof(*devices), GFP_KERNEL); + if (!devices) + return -ENOMEM; + + fill.devices = devices; + fill.nr_devices = count; fill.vdev = &vdev->vdev;
if (vfio_device_cdev_opened(&vdev->vdev)) @@ -1291,16 +1304,23 @@ static int vfio_pci_ioctl_get_pci_hot_reset_info( &fill, slot); mutex_unlock(&vdev->vdev.dev_set->lock); if (ret) - return ret; + goto out; + + if (copy_to_user(arg->devices, devices, + sizeof(*devices) * fill.count)) { + ret = -EFAULT; + goto out; + }
hdr.count = fill.count; hdr.flags = fill.flags; - if (copy_to_user(arg, &hdr, minsz)) - return -EFAULT;
- if (fill.count > fill.devices - arg->devices) - return -ENOSPC; - return 0; +header: + if (copy_to_user(arg, &hdr, minsz)) + ret = -EFAULT; +out: + kfree(devices); + return ret; }
static int