Tim Deegan
2010-Oct-29 14:02 UTC
[Xen-devel] [PATCH] Xen: fix various checks of unsigned integers < 0
# HG changeset patch
# User Tim Deegan <Tim.Deegan@citrix.com>
# Date 1288360674 -3600
# Node ID 52ce5ef855cf2582749d2d0812754ac074cc14e9
# Parent 3cc0fac4a49e29ca0b841c8354a0a9c0686e3d58
Xen: fix various checks of unsigned integers < 0
Some of these could be benignly discarded by the compiler but some are
actual bugs.
Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
diff -r 3cc0fac4a49e -r 52ce5ef855cf xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Fri Oct 29 14:57:50 2010 +0100
+++ b/xen/arch/x86/mm.c Fri Oct 29 14:57:54 2010 +0100
@@ -4533,7 +4533,7 @@ static int handle_iomem_range(unsigned l
ent.size = (uint64_t)(s - ctxt->s) << PAGE_SHIFT;
ent.type = E820_RESERVED;
buffer = guest_handle_cast(ctxt->map.buffer, e820entry_t);
- if ( __copy_to_guest_offset(buffer, ctxt->n, &ent, 1) < 0 )
+ if ( __copy_to_guest_offset(buffer, ctxt->n, &ent, 1) )
return -EFAULT;
ctxt->n++;
}
@@ -4750,7 +4750,7 @@ long arch_memory_op(int op, XEN_GUEST_HA
}
if ( ctxt.map.nr_entries <= ctxt.n + (e820.nr_map - i) )
return -EINVAL;
- if ( __copy_to_guest_offset(buffer, ctxt.n, e820.map + i, 1) < 0
)
+ if ( __copy_to_guest_offset(buffer, ctxt.n, e820.map + i, 1) )
return -EFAULT;
ctxt.s = PFN_UP(e820.map[i].addr + e820.map[i].size);
}
diff -r 3cc0fac4a49e -r 52ce5ef855cf xen/arch/x86/physdev.c
--- a/xen/arch/x86/physdev.c Fri Oct 29 14:57:50 2010 +0100
+++ b/xen/arch/x86/physdev.c Fri Oct 29 14:57:54 2010 +0100
@@ -202,7 +202,7 @@ ret_t do_physdev_op(int cmd, XEN_GUEST_H
if ( copy_from_guest(&eoi, arg, 1) != 0 )
break;
ret = -EINVAL;
- if ( eoi.irq < 0 || eoi.irq >= v->domain->nr_pirqs )
+ if ( eoi.irq >= v->domain->nr_pirqs )
break;
if ( v->domain->arch.pirq_eoi_map )
evtchn_unmask(v->domain->pirq_to_evtchn[eoi.irq]);
diff -r 3cc0fac4a49e -r 52ce5ef855cf xen/arch/x86/platform_hypercall.c
--- a/xen/arch/x86/platform_hypercall.c Fri Oct 29 14:57:50 2010 +0100
+++ b/xen/arch/x86/platform_hypercall.c Fri Oct 29 14:57:54 2010 +0100
@@ -418,7 +418,6 @@ ret_t do_platform_op(XEN_GUEST_HANDLE(xe
}
if ( (g_info->xen_cpuid >= NR_CPUS) ||
- (g_info->xen_cpuid < 0) ||
!cpu_present(g_info->xen_cpuid) )
{
g_info->flags |= XEN_PCPU_FLAGS_INVALID;
diff -r 3cc0fac4a49e -r 52ce5ef855cf xen/arch/x86/x86_emulate/x86_emulate.c
--- a/xen/arch/x86/x86_emulate/x86_emulate.c Fri Oct 29 14:57:50 2010 +0100
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c Fri Oct 29 14:57:54 2010 +0100
@@ -2102,7 +2102,7 @@ x86_emulate(
_regs.edx = (uint32_t)(((int32_t)_regs.eax < 0) ? -1 : 0);
break;
case 8:
- _regs.edx = (_regs.eax < 0) ? -1 : 0;
+ _regs.edx = ((int64_t)_regs.eax < 0) ? -1 : 0;
break;
}
break;
diff -r 3cc0fac4a49e -r 52ce5ef855cf xen/drivers/cpufreq/cpufreq.c
--- a/xen/drivers/cpufreq/cpufreq.c Fri Oct 29 14:57:50 2010 +0100
+++ b/xen/drivers/cpufreq/cpufreq.c Fri Oct 29 14:57:54 2010 +0100
@@ -116,8 +116,7 @@ int cpufreq_limit_change(unsigned int cp
!processor_pminfo[cpu])
return -ENODEV;
- if ((perf->platform_limit < 0) ||
- (perf->platform_limit >= perf->state_count))
+ if (perf->platform_limit >= perf->state_count)
return -EINVAL;
memcpy(&policy, data, sizeof(struct cpufreq_policy));
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Dan Magenheimer
2010-Oct-29 15:38 UTC
RE: [Xen-devel] [PATCH] Xen: fix various checks of unsigned integers < 0
> diff -r 3cc0fac4a49e -r 52ce5ef855cf > xen/arch/x86/x86_emulate/x86_emulate.c > --- a/xen/arch/x86/x86_emulate/x86_emulate.c Fri Oct 29 14:57:50 > 2010 +0100 > +++ b/xen/arch/x86/x86_emulate/x86_emulate.c Fri Oct 29 14:57:54 > 2010 +0100 > @@ -2102,7 +2102,7 @@ x86_emulate( > _regs.edx = (uint32_t)(((int32_t)_regs.eax < 0) ? -1 : 0); > break; > case 8: > - _regs.edx = (_regs.eax < 0) ? -1 : 0; > + _regs.edx = ((int64_t)_regs.eax < 0) ? -1 : 0; > break; > } > break;(/me goes and looks up the cwd instruction...) Wow, I wonder how many times this code has executed and returned the wrong (incorrectly sign-extended) value? Talk about a possible silent-but-deadly bug that would be impossible to track down! Nice catch! Future Xen support people thank you! _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Paolo Bonzini
2010-Oct-29 21:23 UTC
[Xen-devel] Re: [PATCH] Xen: fix various checks of unsigned integers < 0
On 10/29/2010 05:38 PM, Dan Magenheimer wrote:> Wow, I wonder how many times this code has executed > and returned the wrong (incorrectly sign-extended) value?Probably never---which doesn''t make the fix worthless, but is still never. :) The emulator is mostly used for real mode and MMIO, but this is long-mode code (which rules out real mode) and the CQO instruction doesn''t access memory (which rules out MMIO). To trigger the bug you probably have to cause a race between a thread doing MMIO and a thread replacing the MMIO instruction with a CQO. It can be done fairly reliably on KVM; until they were patched, this trick allowed to exploit emulator bugs and go from guest-ring3 to guest-ring0. Paolo _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel