diff mbox series

x86/PV: don't use access_ok() in set_debugreg()

Message ID f2e73d5e-209c-235c-9fad-7d541aa38382@suse.com (mailing list archive)
State Superseded
Headers show
Series x86/PV: don't use access_ok() in set_debugreg() | expand

Commit Message

Jan Beulich Sept. 5, 2023, 9:01 a.m. UTC 
access_ok() is not be applicable here; we really only want a linear
address check for breakpoint addresses, as putting those in debug
register isn't going to result in actual memory accesses. Furthermore
access_ok() assumes to be acting on current, which isn't the case here
when called from arch_set_info_guest().

Note that access_ok() was too lax anyway for 32-bit domains.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
The questionable use of sizeof(long) is left in place for the moment,
as it's not clear how to best deal with the upper bound of breakpoint
covered ranges: We'd like those to not cover Xen space.
diff mbox series

Patch

--- a/xen/arch/x86/pv/misc-hypercalls.c
+++ b/xen/arch/x86/pv/misc-hypercalls.c
@@ -60,7 +60,10 @@  long set_debugreg(struct vcpu *v, unsign
     switch ( reg )
     {
     case 0 ... 3:
-        if ( !access_ok(value, sizeof(long)) )
+        if ( is_pv_32bit_vcpu(v)
+             ? value + sizeof(long) > HYPERVISOR_COMPAT_VIRT_START(v->domain)
+             : value + sizeof(long) > (1UL << (VADDR_BITS - 1)) &&
+               value < HYPERVISOR_VIRT_END )
             return -EPERM;
 
         v->arch.dr[reg] = value;