btrfs-progs: lowmem check: Fix function call stack overflow caused by wrong tree...

For reloc tree root, its backref points to itself.  So for such case,
we should finish the lookup.

Previous end condition is to ensure it's reloc tree *and* needs its root
bytenr to match the bytenr passed in.

However the @root passed can be another tree, e.g. other tree reloc root
which shares the node/leaf.  This makes any check based on @root passed
in invalid.

The patch removes the unreliable root objectid detection, and only uses
root->bytenr check.
For the possibility of invalid self-pointing backref, extent tree
checker should have already handled it, so we don't need to bother in
fs tree checker.

Fixes: 54c8f9152fd9 ("btrfs-progs: check: Fix lowmem mode stack overflow caused by fsck/023")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/cmds-check.c b/cmds-check.c
index 452e715..7eb08b6 100644 (file)
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -11700,16 +11700,12 @@ static int check_tree_block_ref(struct btrfs_root *root,
        u32 nodesize = root->fs_info->nodesize;
        u32 item_size;
        u64 offset;
-       int tree_reloc_root = 0;
        int found_ref = 0;
        int err = 0;
        int ret;
        int strict = 1;
        int parent = 0;
 
-       if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
-           btrfs_header_bytenr(root->node) == bytenr)
-               tree_reloc_root = 1;
        btrfs_init_path(&path);
        key.objectid = bytenr;
        if (btrfs_fs_incompat(root->fs_info, SKINNY_METADATA))
@@ -11817,8 +11813,12 @@ static int check_tree_block_ref(struct btrfs_root *root,
                        /*
                         * Backref of tree reloc root points to itself, no need
                         * to check backref any more.
+                        *
+                        * This may be an error of loop backref, but extent tree
+                        * checker should have already handled it.
+                        * Here we only need to avoid infinite iteration.
                         */
-                       if (tree_reloc_root) {
+                       if (offset == bytenr) {
                                found_ref = 1;
                        } else {
                                /*