RDMA/nes: Fix off-by-one in nes_reg_user_mr() error path

nes_reg_user_mr() should fail if page_count becomes >= 1024 * 512
rather than just testing for strict >, because page_count is
essentially used as an index into an array with 1024 * 512 entries, so
allowing the loop to continue with page_count == 1024 * 512 means that
memory after the end of the array is corrupted.  This leads to a crash
triggerable by a userspace application that requests registration of a
too-big region.

Also get rid of the call to pci_free_consistent() here to avoid
corrupting state with a double free, since the same memory will be
freed in the code jumped to at reg_user_mr_err.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/nes/nes_verbs.c

@@ -2456,10 +2456,8 @@ static struct ib_mr *nes_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 						if ((page_count!=0)&&(page_count<<12)-(region->offset&(4096-1))>=region->length)
 							goto enough_pages;
 						if ((page_count&0x01FF) == 0) {
-							if (page_count>(1024*512)) {
+							if (page_count >= 1024 * 512) {
 								ib_umem_release(region);
-								pci_free_consistent(nesdev->pcidev, 4096, vpbl.pbl_vbase,
-										vpbl.pbl_pbase);
 								nes_free_resource(nesadapter,
 										nesadapter->allocated_mrs, stag_index);
 								kfree(nesmr);