[dfs] fixup: file_mmap and page cache

Including cache maintenance, potential dereference of null pointer and
the use-after-free issue in page cache

Signed-off-by: shell <smokewood@qq.com>

components/dfs/dfs_v2/src/dfs_file_mmap.c

@@ -272,7 +272,7 @@ rt_err_t on_varea_shrink(struct rt_varea *varea, void *new_vaddr, rt_size_t size
         rm_start = varea_start + size;
         rm_end = varea_start + varea->size;
     }
-    else if (varea_start < (char *)new_vaddr)
+    else
     {
         rm_start = varea_start;
         rm_end = new_vaddr;
@@ -293,6 +293,7 @@ rt_err_t on_varea_expand(struct rt_varea *varea, void *new_vaddr, rt_size_t size
 
 rt_err_t on_varea_split(struct rt_varea *existed, void *unmap_start, rt_size_t unmap_len, struct rt_varea *subset)
 {
+    rt_err_t rc;
     struct dfs_file *file = dfs_mem_obj_get_file(existed->mem_obj);
 
     if (file)
@@ -307,12 +308,15 @@ rt_err_t on_varea_split(struct rt_varea *existed, void *unmap_start, rt_size_t u
             LOG_I("file: %s%s", file->dentry->mnt->fullpath, file->dentry->pathname);
         }
 
-        unmap_pages(existed, unmap_start, (char *)unmap_start + unmap_len);
+        rc = unmap_pages(existed, unmap_start, (char *)unmap_start + unmap_len);
+        if (!rc)
+        {
+            rc = unmap_pages(existed, subset->start, (char *)subset->start + subset->size);
+            if (!rc)
+                on_varea_open(subset);
+        }
 
-        subset->data = existed->data;
+        return rc;
-        rt_atomic_add(&(file->ref_count), 1);
-
-        return RT_EOK;
     }
     else
     {
@@ -338,8 +342,7 @@ rt_err_t on_varea_merge(struct rt_varea *merge_to, struct rt_varea *merge_from)
         }
 
         dfs_aspace_unmap(file, merge_from);
-        merge_from->data = RT_NULL;
+        on_varea_close(merge_from);
-        rt_atomic_sub(&(file->ref_count), 1);
 
         return RT_EOK;
     }
@@ -406,7 +409,9 @@ int dfs_file_mmap(struct dfs_file *file, struct dfs_mmap2_args *mmap2)
 
     LOG_I("mmap2 args addr: %p length: 0x%x prot: %d flags: 0x%x pgoffset: 0x%x",
            mmap2->addr, mmap2->length, mmap2->prot, mmap2->flags, mmap2->pgoffset);
-    if (file && file->vnode && file->vnode->aspace)
+    if (file && file->vnode)
+    {
+        if (file->vnode->aspace)
         {
             /* create a va area in user space (lwp) */
             rt_varea_t varea = dfs_map_user_varea_data(mmap2, file);
@@ -424,10 +429,11 @@ int dfs_file_mmap(struct dfs_file *file, struct dfs_mmap2_args *mmap2)
                 ret = -ENOMEM;
             }
         }
-    else if (file->vnode->aspace == RT_NULL)
+        else
         {
             LOG_E("File mapping is not supported, file: %s%s", file->dentry->mnt->fullpath, file->dentry->pathname);
         }
+    }
 
     return ret;
 }

components/dfs/dfs_v2/src/dfs_pcache.c

@@ -6,6 +6,7 @@
  * Change Logs:
  * Date           Author       Notes
  * 2023-05-05     RTT          Implement mnt in dfs v2.0
+ * 2023-10-23     Shell        fix synchronization of data to icache
  */
 
 #include "dfs_pcache.h"
@@ -15,6 +16,8 @@
 #include <mmu.h>
 #include <tlb.h>
 
+#include <rthw.h>
+
 #ifdef RT_USING_PAGECACHE
 
 #define DBG_TAG "dfs.pcache"
@@ -1270,6 +1273,21 @@ void *dfs_aspace_mmap(struct dfs_file *file, struct rt_varea *varea, void *vaddr
             int err = rt_varea_map_range(varea, vaddr, pg_paddr, page->size);
             if (err == RT_EOK)
             {
+                /**
+                 * Note: While the page is mapped into user area, the data writing into the page
+                 * is not guaranteed to be visible for machines with the *weak* memory model and
+                 * those Harvard architecture (especially for those ARM64) cores for their
+                 * out-of-order pipelines of data buffer. Besides if the instruction cache in the
+                 * L1 memory system is a VIPT cache, there are chances to have the alias matching
+                 * entry if we reuse the same page frame and map it into the same virtual address
+                 * of the previous one.
+                 *
+                 * That's why we have to do synchronization and cleanup manually to ensure that
+                 * fetching of the next instruction can see the coherent data with the data cache,
+                 * TLB, MMU, main memory, and all the other observers in the computer system.
+                 */
+                rt_hw_cpu_icache_ops(RT_HW_CACHE_INVALIDATE, vaddr, ARCH_PAGE_SIZE);
+
                 ret = page->page;
                 map->varea = varea;
                 dfs_aspace_lock(aspace);
@@ -1358,6 +1376,7 @@ int dfs_aspace_page_unmap(struct dfs_file *file, struct rt_varea *varea, void *v
         {
             rt_list_t *node, *tmp;
             struct dfs_mmap *map;
+            rt_varea_unmap_page(varea, vaddr);
 
             node = page->mmap_head.next;