btrfs: tree-checker: fix false alert caused by legacy btrfs root item

Commit 259ee7754b67 ("btrfs: tree-checker: Add ROOT_ITEM check")
introduced btrfs root item size check, however btrfs root item has two
versions, the legacy one which just ends before generation_v2 member, is
smaller than current btrfs root item size.

This caused btrfs kernel to reject valid but old tree root leaves.

Fix this problem by also allowing legacy root item, since kernel can
already handle them pretty well and upgrade to newer root item format
when needed.

Reported-by: Martin Steigerwald <martin@lichtvoll.de>
Fixes: 259ee7754b67 ("btrfs: tree-checker: Add ROOT_ITEM check")
CC: stable@vger.kernel.org # 5.4+
Tested-By: Martin Steigerwald <martin@lichtvoll.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 7b1fee630f97851a35eb0bb34d33d95d1e31b991..f0ffd5ee77bd5700847bb580417a3f3242f88630 100644 (file)
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -1035,7 +1035,7 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
                           int slot)
 {
        struct btrfs_fs_info *fs_info = leaf->fs_info;
-       struct btrfs_root_item ri;
+       struct btrfs_root_item ri = { 0 };
        const u64 valid_root_flags = BTRFS_ROOT_SUBVOL_RDONLY |
                                     BTRFS_ROOT_SUBVOL_DEAD;
        int ret;
@@ -1044,14 +1044,21 @@ static int check_root_item(struct extent_buffer *leaf, struct btrfs_key *key,
        if (ret < 0)
                return ret;
 
-       if (btrfs_item_size_nr(leaf, slot) != sizeof(ri)) {
+       if (btrfs_item_size_nr(leaf, slot) != sizeof(ri) &&
+           btrfs_item_size_nr(leaf, slot) != btrfs_legacy_root_item_size()) {
                generic_err(leaf, slot,
-                           "invalid root item size, have %u expect %zu",
-                           btrfs_item_size_nr(leaf, slot), sizeof(ri));
+                           "invalid root item size, have %u expect %zu or %u",
+                           btrfs_item_size_nr(leaf, slot), sizeof(ri),
+                           btrfs_legacy_root_item_size());
        }
 
+       /*
+        * For legacy root item, the members starting at generation_v2 will be
+        * all filled with 0.
+        * And since we allow geneartion_v2 as 0, it will still pass the check.
+        */
        read_extent_buffer(leaf, &ri, btrfs_item_ptr_offset(leaf, slot),
-                          sizeof(ri));
+                          btrfs_item_size_nr(leaf, slot));
 
        /* Generation related */
        if (btrfs_root_generation(&ri) >

diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index 9ba64ca6b4ac953310d014ef9d4e3e6719f258b0..6b885982ece68775a97941b5b495d5b551609d2e 100644 (file)
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -4,6 +4,11 @@
 
 #include <linux/btrfs.h>
 #include <linux/types.h>
+#ifdef __KERNEL__
+#include <linux/stddef.h>
+#else
+#include <stddef.h>
+#endif
 
 /*
  * This header contains the structure definitions and constants used
@@ -644,6 +649,15 @@ struct btrfs_root_item {
        __le64 reserved[8]; /* for future */
 } __attribute__ ((__packed__));
 
+/*
+ * Btrfs root item used to be smaller than current size.  The old format ends
+ * at where member generation_v2 is.
+ */
+static inline __u32 btrfs_legacy_root_item_size(void)
+{
+       return offsetof(struct btrfs_root_item, generation_v2);
+}
+
 /*
  * this is used for both forward and backward root refs
  */