staging: tidspbridge: protect dmm_map properly

We need to protect not only the dmm_map list, but the individual
map_obj's, otherwise, we might be building the scatter-gather list with
garbage. So, use the existing proc_lock for that.

I observed race conditions which caused kernel panics while running
stress tests, also, Tuomas Kulve found it happening quite often in
Gumstix Over. This patch fixes those.

Cc: Tuomas Kulve <tuomas@kulve.fi>
Signed-off-by: Felipe Contreras <felipe.contreras@nokia.com>
Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/tidspbridge/rmgr/proc.c

@@ -779,12 +779,14 @@ int proc_begin_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
 							(u32)pmpu_addr,
 							ul_size, dir);
 
+	mutex_lock(&proc_lock);
+
 	/* find requested memory are in cached mapping information */
 	map_obj = find_containing_mapping(pr_ctxt, (u32) pmpu_addr, ul_size);
 	if (!map_obj) {
 		pr_err("%s: find_containing_mapping failed\n", __func__);
 		status = -EFAULT;
-		goto err_out;
+		goto no_map;
 	}
 
 	if (memory_give_ownership(map_obj, (u32) pmpu_addr, ul_size, dir)) {
@@ -793,6 +795,8 @@ int proc_begin_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
 		status = -EFAULT;
 	}
 
+no_map:
+	mutex_unlock(&proc_lock);
 err_out:
 
 	return status;
@@ -817,21 +821,24 @@ int proc_end_dma(void *hprocessor, void *pmpu_addr, u32 ul_size,
 							(u32)pmpu_addr,
 							ul_size, dir);
 
+	mutex_lock(&proc_lock);
+
 	/* find requested memory are in cached mapping information */
 	map_obj = find_containing_mapping(pr_ctxt, (u32) pmpu_addr, ul_size);
 	if (!map_obj) {
 		pr_err("%s: find_containing_mapping failed\n", __func__);
 		status = -EFAULT;
-		goto err_out;
+		goto no_map;
 	}
 
 	if (memory_regain_ownership(map_obj, (u32) pmpu_addr, ul_size, dir)) {
 		pr_err("%s: InValid address parameters %p %x\n",
 		       __func__, pmpu_addr, ul_size);
 		status = -EFAULT;
-		goto err_out;
 	}
 
+no_map:
+	mutex_unlock(&proc_lock);
 err_out:
 	return status;
 }
@@ -1724,9 +1731,8 @@ int proc_un_map(void *hprocessor, void *map_addr,
 		    (p_proc_object->bridge_context, va_align, size_align);
 	}
 
-	mutex_unlock(&proc_lock);
 	if (status)
-		goto func_end;
+		goto unmap_failed;
 
 	/*
 	 * A successful unmap should be followed by removal of map_obj
@@ -1735,6 +1741,9 @@ int proc_un_map(void *hprocessor, void *map_addr,
 	 */
 	remove_mapping_information(pr_ctxt, (u32) map_addr, size_align);
 
+unmap_failed:
+	mutex_unlock(&proc_lock);
+
 func_end:
 	dev_dbg(bridge, "%s: hprocessor: 0x%p map_addr: 0x%p status: 0x%x\n",
 		__func__, hprocessor, map_addr, status);