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    Subject[PATCH 5.19 03/33] nilfs2: fix leak of nilfs_root in case of writer thread creation failure
    Date
    From: Ryusuke Konishi <konishi.ryusuke@gmail.com>

    commit d0d51a97063db4704a5ef6bc978dddab1636a306 upstream.

    If nilfs_attach_log_writer() failed to create a log writer thread, it
    frees a data structure of the log writer without any cleanup. After
    commit e912a5b66837 ("nilfs2: use root object to get ifile"), this causes
    a leak of struct nilfs_root, which started to leak an ifile metadata inode
    and a kobject on that struct.

    In addition, if the kernel is booted with panic_on_warn, the above
    ifile metadata inode leak will cause the following panic when the
    nilfs2 kernel module is removed:

    kmem_cache_destroy nilfs2_inode_cache: Slab cache still has objects when
    called from nilfs_destroy_cachep+0x16/0x3a [nilfs2]
    WARNING: CPU: 8 PID: 1464 at mm/slab_common.c:494 kmem_cache_destroy+0x138/0x140
    ...
    RIP: 0010:kmem_cache_destroy+0x138/0x140
    Code: 00 20 00 00 e8 a9 55 d8 ff e9 76 ff ff ff 48 8b 53 60 48 c7 c6 20 70 65 86 48 c7 c7 d8 69 9c 86 48 8b 4c 24 28 e8 ef 71 c7 00 <0f> 0b e9 53 ff ff ff c3 48 81 ff ff 0f 00 00 77 03 31 c0 c3 53 48
    ...
    Call Trace:
    <TASK>
    ? nilfs_palloc_freev.cold.24+0x58/0x58 [nilfs2]
    nilfs_destroy_cachep+0x16/0x3a [nilfs2]
    exit_nilfs_fs+0xa/0x1b [nilfs2]
    __x64_sys_delete_module+0x1d9/0x3a0
    ? __sanitizer_cov_trace_pc+0x1a/0x50
    ? syscall_trace_enter.isra.19+0x119/0x190
    do_syscall_64+0x34/0x80
    entry_SYSCALL_64_after_hwframe+0x63/0xcd
    ...
    </TASK>
    Kernel panic - not syncing: panic_on_warn set ...

    This patch fixes these issues by calling nilfs_detach_log_writer() cleanup
    function if spawning the log writer thread fails.

    Link: https://lkml.kernel.org/r/20221007085226.57667-1-konishi.ryusuke@gmail.com
    Fixes: e912a5b66837 ("nilfs2: use root object to get ifile")
    Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
    Reported-by: syzbot+7381dc4ad60658ca4c05@syzkaller.appspotmail.com
    Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/nilfs2/segment.c | 7 +++----
    1 file changed, 3 insertions(+), 4 deletions(-)

    --- a/fs/nilfs2/segment.c
    +++ b/fs/nilfs2/segment.c
    @@ -2786,10 +2786,9 @@ int nilfs_attach_log_writer(struct super
    inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL);

    err = nilfs_segctor_start_thread(nilfs->ns_writer);
    - if (err) {
    - kfree(nilfs->ns_writer);
    - nilfs->ns_writer = NULL;
    - }
    + if (unlikely(err))
    + nilfs_detach_log_writer(sb);
    +
    return err;
    }


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