[PATCH 5.10 067/112] sfc: fix use after free when disabling sriov

Greg Kroah-Hartman
2022-07-19T12:24:58Z

From: Íñigo Huguet <ihuguet@redhat.com>

[ Upstream commit ebe41da5d47ac0fff877e57bd14c54dccf168827 ]

Use after free is detected by kfence when disabling sriov. What was read
after being freed was vf->pci_dev: it was freed from pci_disable_sriov
and later read in efx_ef10_sriov_free_vf_vports, called from
efx_ef10_sriov_free_vf_vswitching.

Set the pointer to NULL at release time to not trying to read it later.

Reproducer and dmesg log (note that kfence doesn't detect it every time):
$ echo 1 > /sys/class/net/enp65s0f0np0/device/sriov_numvfs
$ echo 0 > /sys/class/net/enp65s0f0np0/device/sriov_numvfs

BUG: KFENCE: use-after-free read in efx_ef10_sriov_free_vf_vswitching+0x82/0x170 [sfc]

Use-after-free read at 0x00000000ff3c1ba5 (in kfence-#224):
efx_ef10_sriov_free_vf_vswitching+0x82/0x170 [sfc]
efx_ef10_pci_sriov_disable+0x38/0x70 [sfc]
efx_pci_sriov_configure+0x24/0x40 [sfc]
sriov_numvfs_store+0xfe/0x140
kernfs_fop_write_iter+0x11c/0x1b0
new_sync_write+0x11f/0x1b0
vfs_write+0x1eb/0x280
ksys_write+0x5f/0xe0
do_syscall_64+0x5c/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

kfence-#224: 0x00000000edb8ef95-0x00000000671f5ce1, size=2792, cache=kmalloc-4k

allocated by task 6771 on cpu 10 at 3137.860196s:
pci_alloc_dev+0x21/0x60
pci_iov_add_virtfn+0x2a2/0x320
sriov_enable+0x212/0x3e0
efx_ef10_sriov_configure+0x67/0x80 [sfc]
efx_pci_sriov_configure+0x24/0x40 [sfc]
sriov_numvfs_store+0xba/0x140
kernfs_fop_write_iter+0x11c/0x1b0
new_sync_write+0x11f/0x1b0
vfs_write+0x1eb/0x280
ksys_write+0x5f/0xe0
do_syscall_64+0x5c/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

freed by task 6771 on cpu 12 at 3170.991309s:
device_release+0x34/0x90
kobject_cleanup+0x3a/0x130
pci_iov_remove_virtfn+0xd9/0x120
sriov_disable+0x30/0xe0
efx_ef10_pci_sriov_disable+0x57/0x70 [sfc]
efx_pci_sriov_configure+0x24/0x40 [sfc]
sriov_numvfs_store+0xfe/0x140
kernfs_fop_write_iter+0x11c/0x1b0
new_sync_write+0x11f/0x1b0
vfs_write+0x1eb/0x280
ksys_write+0x5f/0xe0
do_syscall_64+0x5c/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 3c5eb87605e85 ("sfc: create vports for VFs and assign random MAC addresses")
Reported-by: Yanghang Liu <yanghliu@redhat.com>
Signed-off-by: Íñigo Huguet <ihuguet@redhat.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20220712062642.6915-1-ihuguet@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/sfc/ef10_sriov.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/sfc/ef10_sriov.c b/drivers/net/ethernet/sfc/ef10_sriov.c
index 84041cd587d7..b44acb6e3953 100644
--- a/drivers/net/ethernet/sfc/ef10_sriov.c
+++ b/drivers/net/ethernet/sfc/ef10_sriov.c
@@ -411,8 +411,9 @@ static int efx_ef10_pci_sriov_enable(struct efx_nic *efx, int num_vfs)
static int efx_ef10_pci_sriov_disable(struct efx_nic *efx, bool force)
{
struct pci_dev *dev = efx->pci_dev;
+ struct efx_ef10_nic_data *nic_data = efx->nic_data;
unsigned int vfs_assigned = pci_vfs_assigned(dev);
- int rc = 0;
+ int i, rc = 0;

if (vfs_assigned && !force) {
netif_info(efx, drv, efx->net_dev, "VFs are assigned to guests; "
@@ -420,10 +421,13 @@ static int efx_ef10_pci_sriov_disable(struct efx_nic *efx, bool force)
return -EBUSY;
}

- if (!vfs_assigned)
+ if (!vfs_assigned) {
+ for (i = 0; i < efx->vf_count; i++)
+ nic_data->vf[i].pci_dev = NULL;
pci_disable_sriov(dev);
- else
+ } else {
rc = -EBUSY;
+ }

efx_ef10_sriov_free_vf_vswitching(efx);
efx->vf_count = 0;
--
2.35.1