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    Subject[PATCH 6.0 122/862] btrfs: set generation before calling btrfs_clean_tree_block in btrfs_init_new_buffer
    Date
    From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

    commit cbddcc4fa3443fe8cfb2ff8e210deb1f6a0eea38 upstream.

    syzbot is reporting uninit-value in btrfs_clean_tree_block() [1], for
    commit bc877d285ca3dba2 ("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 [1]
    Reported-by: syzbot <syzbot+fba8e2116a12609b6c59@syzkaller.appspotmail.com>
    Fixes: bc877d285ca3dba2 ("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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/btrfs/extent-tree.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/fs/btrfs/extent-tree.c
    +++ b/fs/btrfs/extent-tree.c
    @@ -4888,6 +4888,9 @@ btrfs_init_new_buffer(struct btrfs_trans
    !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

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