[JFFS2] Don't trust node headers before the CRC is checked.

Especially when summary code is used, we can have in-memory data
structures referencing certain nodes without them actually being readable
on the flash. Discard the nodes gracefully in that case, rather than
triggering a BUG().

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

1 files changed, 34 insertions, 28 deletions

diff --git a/fs/jffs2/readinode.c b/fs/jffs2/readinode.c
index e1acce8fb2b..5351b34d541 100644
--- a/fs/jffs2/readinode.c
+++ b/fs/jffs2/readinode.c
@@ -343,7 +343,7 @@ free_out:
  * Helper function for jffs2_get_inode_nodes().
  * It is called every time an unknown node is found.
  *
- * Returns: 0 on succes;
+ * Returns: 0 on success;
  *          1 if the node should be marked obsolete;
  *          negative error code on failure.
  */
@@ -354,37 +354,30 @@ static inline int read_unknown(struct jffs2_sb_info *c, struct jffs2_raw_node_re
 
         un->nodetype = cpu_to_je16(JFFS2_NODE_ACCURATE | je16_to_cpu(un->nodetype));
 
-        if (crc32(0, un, sizeof(struct jffs2_unknown_node) - 4) != je32_to_cpu(un->hdr_crc)) {
-                /* Hmmm. This should have been caught at scan time. */
-                JFFS2_NOTICE("node header CRC failed at %#08x. But it must have been OK earlier.\n", ref_offset(ref));
-                jffs2_dbg_dump_node(c, ref_offset(ref));
-                return 1;
-        } else {
-                switch(je16_to_cpu(un->nodetype) & JFFS2_COMPAT_MASK) {
+        switch(je16_to_cpu(un->nodetype) & JFFS2_COMPAT_MASK) {
 
-                case JFFS2_FEATURE_INCOMPAT:
-                        JFFS2_ERROR("unknown INCOMPAT nodetype %#04X at %#08x\n",
-                                je16_to_cpu(un->nodetype), ref_offset(ref));
-                        /* EEP */
-                        BUG();
-                        break;
+        case JFFS2_FEATURE_INCOMPAT:
+                JFFS2_ERROR("unknown INCOMPAT nodetype %#04X at %#08x\n",
+                            je16_to_cpu(un->nodetype), ref_offset(ref));
+                /* EEP */
+                BUG();
+                break;
 
-                case JFFS2_FEATURE_ROCOMPAT:
-                        JFFS2_ERROR("unknown ROCOMPAT nodetype %#04X at %#08x\n",
-                                        je16_to_cpu(un->nodetype), ref_offset(ref));
-                        BUG_ON(!(c->flags & JFFS2_SB_FLAG_RO));
-                        break;
+        case JFFS2_FEATURE_ROCOMPAT:
+                JFFS2_ERROR("unknown ROCOMPAT nodetype %#04X at %#08x\n",
+                            je16_to_cpu(un->nodetype), ref_offset(ref));
+                BUG_ON(!(c->flags & JFFS2_SB_FLAG_RO));
+                break;
 
-                case JFFS2_FEATURE_RWCOMPAT_COPY:
-                        JFFS2_NOTICE("unknown RWCOMPAT_COPY nodetype %#04X at %#08x\n",
-                                        je16_to_cpu(un->nodetype), ref_offset(ref));
-                        break;
+        case JFFS2_FEATURE_RWCOMPAT_COPY:
+                JFFS2_NOTICE("unknown RWCOMPAT_COPY nodetype %#04X at %#08x\n",
+                             je16_to_cpu(un->nodetype), ref_offset(ref));
+                break;
 
-                case JFFS2_FEATURE_RWCOMPAT_DELETE:
-                        JFFS2_NOTICE("unknown RWCOMPAT_DELETE nodetype %#04X at %#08x\n",
-                                        je16_to_cpu(un->nodetype), ref_offset(ref));
-                        return 1;
-                }
+        case JFFS2_FEATURE_RWCOMPAT_DELETE:
+                JFFS2_NOTICE("unknown RWCOMPAT_DELETE nodetype %#04X at %#08x\n",
+                             je16_to_cpu(un->nodetype), ref_offset(ref));
+                return 1;
         }
 
         return 0;
@@ -549,6 +542,18 @@ static int jffs2_get_inode_nodes(struct jffs2_sb_info *c, struct jffs2_inode_inf
 
                 node = (union jffs2_node_union *)bufstart;
 
+                /* No need to mask in the valid bit; it shouldn't be invalid */
+                if (je32_to_cpu(node->u.hdr_crc) != crc32(0, node, sizeof(node->u)-4)) {
+                        JFFS2_NOTICE("Node header CRC failed at %#08x. {%04x,%04x,%08x,%08x}\n",
+                                     ref_offset(ref), je16_to_cpu(node->u.magic),
+                                     je16_to_cpu(node->u.nodetype),
+                                     je32_to_cpu(node->u.totlen),
+                                     je32_to_cpu(node->u.hdr_crc));
+                        jffs2_dbg_dump_node(c, ref_offset(ref));
+                        jffs2_mark_node_obsolete(c, ref);
+                        goto cont;
+                }
+
                 switch (je16_to_cpu(node->u.nodetype)) {
 
                 case JFFS2_NODETYPE_DIRENT:
@@ -606,6 +611,7 @@ static int jffs2_get_inode_nodes(struct jffs2_sb_info *c, struct jffs2_inode_inf
                                 goto free_out;
 
                 }
+        cont:
                 spin_lock(&c->erase_completion_lock);
         }