btrfs: set generation before calling btrfs_clean_tree_block in btrfs_init_new_buffer

syzbot is reporting uninit-value in btrfs_clean_tree_block() [1], for
commit 7347054c035ee7be ("btrfs: Deduplicate extent_buffer init code")
missed that btrfs_set_header_generation() in btrfs_init_new_buffer() must
not be moved to after clean_tree_block() because clean_tree_block() is
calling btrfs_header_generation() since commit 55c69072d6bd5be1 ("Btrfs:
Fix extent_buffer usage when nodesize != leafsize").

Since memzero_extent_buffer() will reset "struct btrfs_header" part, we
can't move btrfs_set_header_generation() to before memzero_extent_buffer().
Just re-add btrfs_set_header_generation() before btrfs_clean_tree_block().

Link: https://syzkaller.appspot.com/bug?extid=fba8e2116a12609b6c59
Reported-by: syzbot <syzbot+fba8e2116a12609b6c59@syzkaller.appspotmail.com>
Fixes: 7347054c035ee7be ("btrfs: Deduplicate extent_buffer init code")
CC: stable@vger.kernel.org # 4.19+
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ae94be318a0f9035309bb52d82d7a46de574cd04..cd2d36580f1ac169fa0724ba2db732f03bfcfe5d 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4890,6 +4890,9 @@ btrfs_init_new_buffer(struct btrfs_trans_handle *trans, struct btrfs_root *root,
            !test_bit(BTRFS_ROOT_RESET_LOCKDEP_CLASS, &root->state))
                lockdep_owner = BTRFS_FS_TREE_OBJECTID;
 
+       /* btrfs_clean_tree_block() accesses generation field. */
+       btrfs_set_header_generation(buf, trans->transid);
+
        /*
         * This needs to stay, because we could allocate a freed block from an
         * old tree into a new tree, so we need to make sure this new block is