compat: support grsecurity with our compat padata implementation

Some SMP kernels don't have PADATA enabled, which means we actually ship
our own copy of it, lifted right out of the kernel. This is completely
insane and stupid, but so it goes with really grotesque "compat/" layers
such as this one. What this amounts to is having to make this upstream
file compile on all kernels back to 3.10. Ouch.

It also means making it compile with whatever other kernels people are
using, such as Grsecurity.

This patch _should_ make this part of the compat layer work with
Grsecurity, but unfortunately I really have no way of knowing, since I
don't actually have access to their source code. I assume, though, if
this doesn't work, I'll receive more complaints and will take another
stab in the dark. The general situation saddens me, as I really liked
that project and wish I could still play with it. Alas.

Fortunately this entire problem with padata will go away, anyway, when we
stop using padata, and move to a better form of multicore processing. But
for now, we add this to work around the issue.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/compat/padata/padata.c b/src/compat/padata/padata.c
index 25836db..ece0ec7 100644
--- a/src/compat/padata/padata.c
+++ b/src/compat/padata/padata.c
@@ -59,7 +59,11 @@ static int padata_cpu_hash(struct parallel_data *pd)
 	pd->seq_nr++;
 	spin_unlock(&pd->seq_lock);
 #else
+#ifdef CONFIG_PAX_REFCOUNT
+	unsigned int seq_nr = atomic_inc_return_unchecked(&pd->seq_nr);
+#else
 	unsigned int seq_nr = atomic_inc_return(&pd->seq_nr);
+#endif
 	cpu_index = seq_nr % cpumask_weight(pd->cpumask.pcpu);
 #endif
 
@@ -427,8 +431,12 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 13, 0)
 	pd->seq_nr = 0;
 #else
+#ifdef CONFIG_PAX_REFCOUNT
+	atomic_set_unchecked(&pd->seq_nr, -1);
+#else
 	atomic_set(&pd->seq_nr, -1);
 #endif
+#endif
 	atomic_set(&pd->reorder_objects, 0);
 	atomic_set(&pd->refcnt, 0);
 	pd->pinst = pinst;