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    Subject[PATCH 4.19 249/323] fuse: truncate pagecache on atomic_o_trunc
    Date
    From: Miklos Szeredi <mszeredi@redhat.com>

    commit 76224355db7570cbe6b6f75c8929a1558828dd55 upstream.

    fuse_finish_open() will be called with FUSE_NOWRITE in case of atomic
    O_TRUNC. This can deadlock with fuse_wait_on_page_writeback() in
    fuse_launder_page() triggered by invalidate_inode_pages2().

    Fix by replacing invalidate_inode_pages2() in fuse_finish_open() with a
    truncate_pagecache() call. This makes sense regardless of FOPEN_KEEP_CACHE
    or fc->writeback cache, so do it unconditionally.

    Reported-by: Xie Yongji <xieyongji@bytedance.com>
    Reported-and-tested-by: syzbot+bea44a5189836d956894@syzkaller.appspotmail.com
    Fixes: e4648309b85a ("fuse: truncate pending writes on O_TRUNC")
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/fuse/file.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/fs/fuse/file.c
    +++ b/fs/fuse/file.c
    @@ -178,12 +178,11 @@ void fuse_finish_open(struct inode *inod

    if (ff->open_flags & FOPEN_DIRECT_IO)
    file->f_op = &fuse_direct_io_file_operations;
    - if (!(ff->open_flags & FOPEN_KEEP_CACHE))
    - invalidate_inode_pages2(inode->i_mapping);
    if (ff->open_flags & FOPEN_STREAM)
    stream_open(inode, file);
    else if (ff->open_flags & FOPEN_NONSEEKABLE)
    nonseekable_open(inode, file);
    +
    if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
    struct fuse_inode *fi = get_fuse_inode(inode);

    @@ -191,10 +190,14 @@ void fuse_finish_open(struct inode *inod
    fi->attr_version = ++fc->attr_version;
    i_size_write(inode, 0);
    spin_unlock(&fc->lock);
    + truncate_pagecache(inode, 0);
    fuse_invalidate_attr(inode);
    if (fc->writeback_cache)
    file_update_time(file);
    + } else if (!(ff->open_flags & FOPEN_KEEP_CACHE)) {
    + invalidate_inode_pages2(inode->i_mapping);
    }
    +
    if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
    fuse_link_write_file(file);
    }

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