[PATCH 3.12 068/118] x86/UV: Fix NULL pointer dereference in uv_flush_tlb_others() if the nobau boot option is used

Greg Kroah-Hartman
2013-12-18T21:31:01Z

From: cpw <cpw@sgi.com>

commit 3eae49ca8954f958b2001ab5643ef302cb7b67c7 upstream.

The SGI UV tlb shootdown code panics the system with a NULL
pointer deference if 'nobau' is specified on the boot
commandline.

uv_flush_tlb_other() gets called for every flush, whether the
BAU is disabled or not. It should not be keeping the s_enters
statistic while the BAU is disabled.

The panic occurs because during initialization
init_per_cpu_tunables() does not set the bcp->statp pointer if
'nobau' was specified.

Signed-off-by: Cliff Wickman <cpw@sgi.com>
Link: http://lkml.kernel.org/r/E1VnzBi-0005yF-MU@eag09.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/platform/uv/tlb_uv.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -1070,12 +1070,13 @@ const struct cpumask *uv_flush_tlb_other
unsigned long status;

bcp = &per_cpu(bau_control, cpu);
- stat = bcp->statp;
- stat->s_enters++;

if (bcp->nobau)
return cpumask;

+ stat = bcp->statp;
+ stat->s_enters++;
+
if (bcp->busy) {
descriptor_status =
read_lmmr(UVH_LB_BAU_SB_ACTIVATION_STATUS_0);