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Subject[PATCH 4.4 72/85] vfio/pci: fix racy on error and request eventfd ctx
Date
From: Zeng Tao <prime.zeng@hisilicon.com>

[ Upstream commit b872d0640840018669032b20b6375a478ed1f923 ]

The vfio_pci_release call will free and clear the error and request
eventfd ctx while these ctx could be in use at the same time in the
function like vfio_pci_request, and it's expected to protect them under
the vdev->igate mutex, which is missing in vfio_pci_release.

This issue is introduced since commit 1518ac272e78 ("vfio/pci: fix memory
leaks of eventfd ctx"),and since commit 5c5866c593bb ("vfio/pci: Clear
error and request eventfd ctx after releasing"), it's very easily to
trigger the kernel panic like this:

[ 9513.904346] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
[ 9513.913091] Mem abort info:
[ 9513.915871] ESR = 0x96000006
[ 9513.918912] EC = 0x25: DABT (current EL), IL = 32 bits
[ 9513.924198] SET = 0, FnV = 0
[ 9513.927238] EA = 0, S1PTW = 0
[ 9513.930364] Data abort info:
[ 9513.933231] ISV = 0, ISS = 0x00000006
[ 9513.937048] CM = 0, WnR = 0
[ 9513.940003] user pgtable: 4k pages, 48-bit VAs, pgdp=0000007ec7d12000
[ 9513.946414] [0000000000000008] pgd=0000007ec7d13003, p4d=0000007ec7d13003, pud=0000007ec728c003, pmd=0000000000000000
[ 9513.956975] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[ 9513.962521] Modules linked in: vfio_pci vfio_virqfd vfio_iommu_type1 vfio hclge hns3 hnae3 [last unloaded: vfio_pci]
[ 9513.972998] CPU: 4 PID: 1327 Comm: bash Tainted: G W 5.8.0-rc4+ #3
[ 9513.980443] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V3.B270.01 05/08/2020
[ 9513.989274] pstate: 80400089 (Nzcv daIf +PAN -UAO BTYPE=--)
[ 9513.994827] pc : _raw_spin_lock_irqsave+0x48/0x88
[ 9513.999515] lr : eventfd_signal+0x6c/0x1b0
[ 9514.003591] sp : ffff800038a0b960
[ 9514.006889] x29: ffff800038a0b960 x28: ffff007ef7f4da10
[ 9514.012175] x27: ffff207eefbbfc80 x26: ffffbb7903457000
[ 9514.017462] x25: ffffbb7912191000 x24: ffff007ef7f4d400
[ 9514.022747] x23: ffff20be6e0e4c00 x22: 0000000000000008
[ 9514.028033] x21: 0000000000000000 x20: 0000000000000000
[ 9514.033321] x19: 0000000000000008 x18: 0000000000000000
[ 9514.038606] x17: 0000000000000000 x16: ffffbb7910029328
[ 9514.043893] x15: 0000000000000000 x14: 0000000000000001
[ 9514.049179] x13: 0000000000000000 x12: 0000000000000002
[ 9514.054466] x11: 0000000000000000 x10: 0000000000000a00
[ 9514.059752] x9 : ffff800038a0b840 x8 : ffff007ef7f4de60
[ 9514.065038] x7 : ffff007fffc96690 x6 : fffffe01faffb748
[ 9514.070324] x5 : 0000000000000000 x4 : 0000000000000000
[ 9514.075609] x3 : 0000000000000000 x2 : 0000000000000001
[ 9514.080895] x1 : ffff007ef7f4d400 x0 : 0000000000000000
[ 9514.086181] Call trace:
[ 9514.088618] _raw_spin_lock_irqsave+0x48/0x88
[ 9514.092954] eventfd_signal+0x6c/0x1b0
[ 9514.096691] vfio_pci_request+0x84/0xd0 [vfio_pci]
[ 9514.101464] vfio_del_group_dev+0x150/0x290 [vfio]
[ 9514.106234] vfio_pci_remove+0x30/0x128 [vfio_pci]
[ 9514.111007] pci_device_remove+0x48/0x108
[ 9514.115001] device_release_driver_internal+0x100/0x1b8
[ 9514.120200] device_release_driver+0x28/0x38
[ 9514.124452] pci_stop_bus_device+0x68/0xa8
[ 9514.128528] pci_stop_and_remove_bus_device+0x20/0x38
[ 9514.133557] pci_iov_remove_virtfn+0xb4/0x128
[ 9514.137893] sriov_disable+0x3c/0x108
[ 9514.141538] pci_disable_sriov+0x28/0x38
[ 9514.145445] hns3_pci_sriov_configure+0x48/0xb8 [hns3]
[ 9514.150558] sriov_numvfs_store+0x110/0x198
[ 9514.154724] dev_attr_store+0x44/0x60
[ 9514.158373] sysfs_kf_write+0x5c/0x78
[ 9514.162018] kernfs_fop_write+0x104/0x210
[ 9514.166010] __vfs_write+0x48/0x90
[ 9514.169395] vfs_write+0xbc/0x1c0
[ 9514.172694] ksys_write+0x74/0x100
[ 9514.176079] __arm64_sys_write+0x24/0x30
[ 9514.179987] el0_svc_common.constprop.4+0x110/0x200
[ 9514.184842] do_el0_svc+0x34/0x98
[ 9514.188144] el0_svc+0x14/0x40
[ 9514.191185] el0_sync_handler+0xb0/0x2d0
[ 9514.195088] el0_sync+0x140/0x180
[ 9514.198389] Code: b9001020 d2800000 52800022 f9800271 (885ffe61)
[ 9514.204455] ---[ end trace 648de00c8406465f ]---
[ 9514.212308] note: bash[1327] exited with preempt_count 1

Cc: Qian Cai <cai@lca.pw>
Cc: Alex Williamson <alex.williamson@redhat.com>
Fixes: 1518ac272e78 ("vfio/pci: fix memory leaks of eventfd ctx")
Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/vfio/pci/vfio_pci.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 662ea7ec82926..8276ef7f3e834 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -255,14 +255,19 @@ static void vfio_pci_release(void *device_data)
if (!(--vdev->refcnt)) {
vfio_spapr_pci_eeh_release(vdev->pdev);
vfio_pci_disable(vdev);
+ mutex_lock(&vdev->igate);
if (vdev->err_trigger) {
eventfd_ctx_put(vdev->err_trigger);
vdev->err_trigger = NULL;
}
+ mutex_unlock(&vdev->igate);
+
+ mutex_lock(&vdev->igate);
if (vdev->req_trigger) {
eventfd_ctx_put(vdev->req_trigger);
vdev->req_trigger = NULL;
}
+ mutex_unlock(&vdev->igate);
}

mutex_unlock(&driver_lock);
--
2.25.1


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