linux/drivers/vfio/pci/vfio_pci_rdwr.c
Alex Williamson abafbc551f vfio-pci: Invalidate mmaps and block MMIO access on disabled memory
Accessing the disabled memory space of a PCI device would typically
result in a master abort response on conventional PCI, or an
unsupported request on PCI express.  The user would generally see
these as a -1 response for the read return data and the write would be
silently discarded, possibly with an uncorrected, non-fatal AER error
triggered on the host.  Some systems however take it upon themselves
to bring down the entire system when they see something that might
indicate a loss of data, such as this discarded write to a disabled
memory space.

To avoid this, we want to try to block the user from accessing memory
spaces while they're disabled.  We start with a semaphore around the
memory enable bit, where writers modify the memory enable state and
must be serialized, while readers make use of the memory region and
can access in parallel.  Writers include both direct manipulation via
the command register, as well as any reset path where the internal
mechanics of the reset may both explicitly and implicitly disable
memory access, and manipulation of the MSI-X configuration, where the
MSI-X vector table resides in MMIO space of the device.  Readers
include the read and write file ops to access the vfio device fd
offsets as well as memory mapped access.  In the latter case, we make
use of our new vma list support to zap, or invalidate, those memory
mappings in order to force them to be faulted back in on access.

Our semaphore usage will stall user access to MMIO spaces across
internal operations like reset, but the user might experience new
behavior when trying to access the MMIO space while disabled via the
PCI command register.  Access via read or write while disabled will
return -EIO and access via memory maps will result in a SIGBUS.  This
is expected to be compatible with known use cases and potentially
provides better error handling capabilities than present in the
hardware, while avoiding the more readily accessible and severe
platform error responses that might otherwise occur.

Fixes: CVE-2020-12888
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
2020-05-18 09:53:38 -06:00

402 lines
8.4 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* VFIO PCI I/O Port & MMIO access
*
* Copyright (C) 2012 Red Hat, Inc. All rights reserved.
* Author: Alex Williamson <alex.williamson@redhat.com>
*
* Derived from original vfio:
* Copyright 2010 Cisco Systems, Inc. All rights reserved.
* Author: Tom Lyon, pugs@cisco.com
*/
#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/vfio.h>
#include <linux/vgaarb.h>
#include "vfio_pci_private.h"
#ifdef __LITTLE_ENDIAN
#define vfio_ioread64 ioread64
#define vfio_iowrite64 iowrite64
#define vfio_ioread32 ioread32
#define vfio_iowrite32 iowrite32
#define vfio_ioread16 ioread16
#define vfio_iowrite16 iowrite16
#else
#define vfio_ioread64 ioread64be
#define vfio_iowrite64 iowrite64be
#define vfio_ioread32 ioread32be
#define vfio_iowrite32 iowrite32be
#define vfio_ioread16 ioread16be
#define vfio_iowrite16 iowrite16be
#endif
#define vfio_ioread8 ioread8
#define vfio_iowrite8 iowrite8
/*
* Read or write from an __iomem region (MMIO or I/O port) with an excluded
* range which is inaccessible. The excluded range drops writes and fills
* reads with -1. This is intended for handling MSI-X vector tables and
* leftover space for ROM BARs.
*/
static ssize_t do_io_rw(void __iomem *io, char __user *buf,
loff_t off, size_t count, size_t x_start,
size_t x_end, bool iswrite)
{
ssize_t done = 0;
while (count) {
size_t fillable, filled;
if (off < x_start)
fillable = min(count, (size_t)(x_start - off));
else if (off >= x_end)
fillable = count;
else
fillable = 0;
if (fillable >= 4 && !(off % 4)) {
u32 val;
if (iswrite) {
if (copy_from_user(&val, buf, 4))
return -EFAULT;
vfio_iowrite32(val, io + off);
} else {
val = vfio_ioread32(io + off);
if (copy_to_user(buf, &val, 4))
return -EFAULT;
}
filled = 4;
} else if (fillable >= 2 && !(off % 2)) {
u16 val;
if (iswrite) {
if (copy_from_user(&val, buf, 2))
return -EFAULT;
vfio_iowrite16(val, io + off);
} else {
val = vfio_ioread16(io + off);
if (copy_to_user(buf, &val, 2))
return -EFAULT;
}
filled = 2;
} else if (fillable) {
u8 val;
if (iswrite) {
if (copy_from_user(&val, buf, 1))
return -EFAULT;
vfio_iowrite8(val, io + off);
} else {
val = vfio_ioread8(io + off);
if (copy_to_user(buf, &val, 1))
return -EFAULT;
}
filled = 1;
} else {
/* Fill reads with -1, drop writes */
filled = min(count, (size_t)(x_end - off));
if (!iswrite) {
u8 val = 0xFF;
size_t i;
for (i = 0; i < filled; i++)
if (copy_to_user(buf + i, &val, 1))
return -EFAULT;
}
}
count -= filled;
done += filled;
off += filled;
buf += filled;
}
return done;
}
static int vfio_pci_setup_barmap(struct vfio_pci_device *vdev, int bar)
{
struct pci_dev *pdev = vdev->pdev;
int ret;
void __iomem *io;
if (vdev->barmap[bar])
return 0;
ret = pci_request_selected_regions(pdev, 1 << bar, "vfio");
if (ret)
return ret;
io = pci_iomap(pdev, bar, 0);
if (!io) {
pci_release_selected_regions(pdev, 1 << bar);
return -ENOMEM;
}
vdev->barmap[bar] = io;
return 0;
}
ssize_t vfio_pci_bar_rw(struct vfio_pci_device *vdev, char __user *buf,
size_t count, loff_t *ppos, bool iswrite)
{
struct pci_dev *pdev = vdev->pdev;
loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
int bar = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
size_t x_start = 0, x_end = 0;
resource_size_t end;
void __iomem *io;
struct resource *res = &vdev->pdev->resource[bar];
ssize_t done;
if (pci_resource_start(pdev, bar))
end = pci_resource_len(pdev, bar);
else if (bar == PCI_ROM_RESOURCE &&
pdev->resource[bar].flags & IORESOURCE_ROM_SHADOW)
end = 0x20000;
else
return -EINVAL;
if (pos >= end)
return -EINVAL;
count = min(count, (size_t)(end - pos));
if (res->flags & IORESOURCE_MEM) {
down_read(&vdev->memory_lock);
if (!__vfio_pci_memory_enabled(vdev)) {
up_read(&vdev->memory_lock);
return -EIO;
}
}
if (bar == PCI_ROM_RESOURCE) {
/*
* The ROM can fill less space than the BAR, so we start the
* excluded range at the end of the actual ROM. This makes
* filling large ROM BARs much faster.
*/
io = pci_map_rom(pdev, &x_start);
if (!io) {
done = -ENOMEM;
goto out;
}
x_end = end;
} else {
int ret = vfio_pci_setup_barmap(vdev, bar);
if (ret) {
done = ret;
goto out;
}
io = vdev->barmap[bar];
}
if (bar == vdev->msix_bar) {
x_start = vdev->msix_offset;
x_end = vdev->msix_offset + vdev->msix_size;
}
done = do_io_rw(io, buf, pos, count, x_start, x_end, iswrite);
if (done >= 0)
*ppos += done;
if (bar == PCI_ROM_RESOURCE)
pci_unmap_rom(pdev, io);
out:
if (res->flags & IORESOURCE_MEM)
up_read(&vdev->memory_lock);
return done;
}
ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
size_t count, loff_t *ppos, bool iswrite)
{
int ret;
loff_t off, pos = *ppos & VFIO_PCI_OFFSET_MASK;
void __iomem *iomem = NULL;
unsigned int rsrc;
bool is_ioport;
ssize_t done;
if (!vdev->has_vga)
return -EINVAL;
if (pos > 0xbfffful)
return -EINVAL;
switch ((u32)pos) {
case 0xa0000 ... 0xbffff:
count = min(count, (size_t)(0xc0000 - pos));
iomem = ioremap(0xa0000, 0xbffff - 0xa0000 + 1);
off = pos - 0xa0000;
rsrc = VGA_RSRC_LEGACY_MEM;
is_ioport = false;
break;
case 0x3b0 ... 0x3bb:
count = min(count, (size_t)(0x3bc - pos));
iomem = ioport_map(0x3b0, 0x3bb - 0x3b0 + 1);
off = pos - 0x3b0;
rsrc = VGA_RSRC_LEGACY_IO;
is_ioport = true;
break;
case 0x3c0 ... 0x3df:
count = min(count, (size_t)(0x3e0 - pos));
iomem = ioport_map(0x3c0, 0x3df - 0x3c0 + 1);
off = pos - 0x3c0;
rsrc = VGA_RSRC_LEGACY_IO;
is_ioport = true;
break;
default:
return -EINVAL;
}
if (!iomem)
return -ENOMEM;
ret = vga_get_interruptible(vdev->pdev, rsrc);
if (ret) {
is_ioport ? ioport_unmap(iomem) : iounmap(iomem);
return ret;
}
done = do_io_rw(iomem, buf, off, count, 0, 0, iswrite);
vga_put(vdev->pdev, rsrc);
is_ioport ? ioport_unmap(iomem) : iounmap(iomem);
if (done >= 0)
*ppos += done;
return done;
}
static int vfio_pci_ioeventfd_handler(void *opaque, void *unused)
{
struct vfio_pci_ioeventfd *ioeventfd = opaque;
switch (ioeventfd->count) {
case 1:
vfio_iowrite8(ioeventfd->data, ioeventfd->addr);
break;
case 2:
vfio_iowrite16(ioeventfd->data, ioeventfd->addr);
break;
case 4:
vfio_iowrite32(ioeventfd->data, ioeventfd->addr);
break;
#ifdef iowrite64
case 8:
vfio_iowrite64(ioeventfd->data, ioeventfd->addr);
break;
#endif
}
return 0;
}
long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
uint64_t data, int count, int fd)
{
struct pci_dev *pdev = vdev->pdev;
loff_t pos = offset & VFIO_PCI_OFFSET_MASK;
int ret, bar = VFIO_PCI_OFFSET_TO_INDEX(offset);
struct vfio_pci_ioeventfd *ioeventfd;
/* Only support ioeventfds into BARs */
if (bar > VFIO_PCI_BAR5_REGION_INDEX)
return -EINVAL;
if (pos + count > pci_resource_len(pdev, bar))
return -EINVAL;
/* Disallow ioeventfds working around MSI-X table writes */
if (bar == vdev->msix_bar &&
!(pos + count <= vdev->msix_offset ||
pos >= vdev->msix_offset + vdev->msix_size))
return -EINVAL;
#ifndef iowrite64
if (count == 8)
return -EINVAL;
#endif
ret = vfio_pci_setup_barmap(vdev, bar);
if (ret)
return ret;
mutex_lock(&vdev->ioeventfds_lock);
list_for_each_entry(ioeventfd, &vdev->ioeventfds_list, next) {
if (ioeventfd->pos == pos && ioeventfd->bar == bar &&
ioeventfd->data == data && ioeventfd->count == count) {
if (fd == -1) {
vfio_virqfd_disable(&ioeventfd->virqfd);
list_del(&ioeventfd->next);
vdev->ioeventfds_nr--;
kfree(ioeventfd);
ret = 0;
} else
ret = -EEXIST;
goto out_unlock;
}
}
if (fd < 0) {
ret = -ENODEV;
goto out_unlock;
}
if (vdev->ioeventfds_nr >= VFIO_PCI_IOEVENTFD_MAX) {
ret = -ENOSPC;
goto out_unlock;
}
ioeventfd = kzalloc(sizeof(*ioeventfd), GFP_KERNEL);
if (!ioeventfd) {
ret = -ENOMEM;
goto out_unlock;
}
ioeventfd->addr = vdev->barmap[bar] + pos;
ioeventfd->data = data;
ioeventfd->pos = pos;
ioeventfd->bar = bar;
ioeventfd->count = count;
ret = vfio_virqfd_enable(ioeventfd, vfio_pci_ioeventfd_handler,
NULL, NULL, &ioeventfd->virqfd, fd);
if (ret) {
kfree(ioeventfd);
goto out_unlock;
}
list_add(&ioeventfd->next, &vdev->ioeventfds_list);
vdev->ioeventfds_nr++;
out_unlock:
mutex_unlock(&vdev->ioeventfds_lock);
return ret;
}