x86: UV BAU: Avoid NULL pointer reference in ptc_seq_show

In init_per_cpu(), when get_cpu_topology() fails, init_per_cpu_tunables()
is not called afterwards. This means that bau_control->statp is NULL.
If a user then reads /proc/sgi_uv/ptc_statistics ptc_seq_show() references
a NULL pointer. Therefore, since uv_bau_init calls set_bau_off when
init_per_cpu() fails, we add code that detects when the bau is off in
ptc_seq_show() to avoid referencing a NULL pointer.

Signed-off-by: James Custer <jcuster@sgi.com>
Cc: Russ Anderson <rja@sgi.com>
Link: http://lkml.kernel.org/r/1414952199-185319-2-git-send-email-jcuster@sgi.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index 3968d67d366bc714231e2f4b2ba864eada762fe6..570b1b14375b1c1482a7467def3e3bbda0a679f3 100644 (file)
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -1384,6 +1384,10 @@ static int ptc_seq_show(struct seq_file *file, void *data)
        }
        if (cpu < num_possible_cpus() && cpu_online(cpu)) {
                bcp = &per_cpu(bau_control, cpu);
+               if (bcp->nobau) {
+                       seq_printf(file, "cpu %d bau disabled\n", cpu);
+                       return 0;
+               }
                stat = bcp->statp;
                /* source side statistics */
                seq_printf(file,