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xen/pt: unknown PCI config space fields should be read-only

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... by default. Add a per-device "permissive" mode similar to pciback's
to allow restoring previous behavior (and hence break security again,
i.e. should be used only for trusted guests).

This is part of XSA-131.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>)
This commit is contained in:
Jan Beulich 2015-06-02 15:07:01 +00:00 committed by Stefano Stabellini
parent a88a3f8871
commit c25bbf1545
3 changed files with 35 additions and 3 deletions
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32
hw/xen/xen_pt.c
View File

@ -239,6 +239,7 @@ static void xen_pt_pci_write_config(PCIDevice *d, uint32_t addr,
XenPTReg *reg_entry = NULL;
uint32_t find_addr = addr;
XenPTRegInfo *reg = NULL;
bool wp_flag = false;
if (xen_pt_pci_config_access_check(d, addr, len)) {
return;
@ -278,6 +279,10 @@ static void xen_pt_pci_write_config(PCIDevice *d, uint32_t addr,
/* pass directly to the real device for passthrough type register group */
if (reg_grp_entry == NULL) {
if (!s->permissive) {
wb_mask = 0;
wp_flag = true;
}
goto out;
}
@ -298,12 +303,15 @@ static void xen_pt_pci_write_config(PCIDevice *d, uint32_t addr,
uint32_t real_offset = reg_grp_entry->base_offset + reg->offset;
uint32_t valid_mask = 0xFFFFFFFF >> ((4 - emul_len) << 3);
uint8_t *ptr_val = NULL;
uint32_t wp_mask = reg->emu_mask | reg->ro_mask;
valid_mask <<= (find_addr - real_offset) << 3;
ptr_val = (uint8_t *)&val + (real_offset & 3);
if (reg->emu_mask == (0xFFFFFFFF >> ((4 - reg->size) << 3))) {
wb_mask &= ~((reg->emu_mask
>> ((find_addr - real_offset) << 3))
if (!s->permissive) {
wp_mask |= reg->res_mask;
}
if (wp_mask == (0xFFFFFFFF >> ((4 - reg->size) << 3))) {
wb_mask &= ~((wp_mask >> ((find_addr - real_offset) << 3))
<< ((len - emul_len) << 3));
}
@ -347,6 +355,16 @@ static void xen_pt_pci_write_config(PCIDevice *d, uint32_t addr,
} else {
/* nothing to do with passthrough type register,
* continue to find next byte */
if (!s->permissive) {
wb_mask &= ~(0xff << ((len - emul_len) << 3));
/* Unused BARs will make it here, but we don't want to issue
* warnings for writes to them (bogus writes get dealt with
* above).
*/
if (index < 0) {
wp_flag = true;
}
}
emul_len--;
find_addr++;
}
@ -358,6 +376,13 @@ static void xen_pt_pci_write_config(PCIDevice *d, uint32_t addr,
memory_region_transaction_commit();
out:
if (wp_flag && !s->permissive_warned) {
s->permissive_warned = true;
xen_pt_log(d, "Write-back to unknown field 0x%02x (partially) inhibited (0x%0*x)\n",
addr, len * 2, wb_mask);
xen_pt_log(d, "If the device doesn't work, try enabling permissive mode\n");
xen_pt_log(d, "(unsafe) and if it helps report the problem to xen-devel\n");
}
for (index = 0; wb_mask; index += len) {
/* unknown regs are passed through */
while (!(wb_mask & 0xff)) {
@ -824,6 +849,7 @@ static void xen_pt_unregister_device(PCIDevice *d)
static Property xen_pci_passthrough_properties[] = {
DEFINE_PROP_PCI_HOST_DEVADDR("hostaddr", XenPCIPassthroughState, hostaddr),
DEFINE_PROP_BOOL("permissive", XenPCIPassthroughState, permissive, false),
DEFINE_PROP_END_OF_LIST(),
};

2
hw/xen/xen_pt.h
View File

@ -197,6 +197,8 @@ struct XenPCIPassthroughState {
PCIHostDeviceAddress hostaddr;
bool is_virtfn;
bool permissive;
bool permissive_warned;
XenHostPCIDevice real_device;
XenPTRegion bases[PCI_NUM_REGIONS]; /* Access regions */
QLIST_HEAD(, XenPTRegGroup) reg_grps;

4
hw/xen/xen_pt_config_init.c
View File

@ -101,6 +101,10 @@ static uint32_t get_throughable_mask(const XenPCIPassthroughState *s,
{
uint32_t throughable_mask = ~(reg->emu_mask | reg->ro_mask);
if (!s->permissive) {
throughable_mask &= ~reg->res_mask;
}
return throughable_mask & valid_mask;
}