RE: Re: [PATCH] fs: initialize resize_wait wait queue of init task

[Daeho Jeong <daeho.jeong@samsung.com>]

> I am curious, what kind of kernel threads are using file table ?
> Thanks.

I don't know all the cases of that.
But, in the embedded world, a lot of device drivers or kernel daemons are
opening the files to just watch and read,
or to write some log data.

 

--------- Original Message ---------

Sender : Eric Dumazet <edumazet@google.com>

Date   : 2017-05-16 23:10 (GMT+9)

Title  : Re: [PATCH] fs: initialize resize_wait wait queue of init task

 

On Mon, May 15, 2017 at 11:40 PM, Daeho Jeong <daeho.jeong@samsung.com> wrote:

> We don't initialize resize_wait of init task now and all the kernel

> threads share this uninitialized resize_wait wait queue because they

> are sharing the file table of init task. Therefore, when expanding

> this file table shared by the kernel threads, we encounter kernel panic

> by accessing the NULL resize_wait wait queue.

>

> Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>

> Tested-by: Youngjin Gil <youngjin.gil@samsung.com>

> ---

>  fs/file.c | 1 +

>  1 file changed, 1 insertion(+)

>

> diff --git a/fs/file.c b/fs/file.c

> index ad6f094f2eff..74748c32e07a 100644

> --- a/fs/file.c

> +++ b/fs/file.c

> @@ -475,6 +475,7 @@ struct files_struct init_files = {

>                 .full_fds_bits  = init_files.full_fds_bits_init,

>         },

>         .file_lock      = __SPIN_LOCK_UNLOCKED(init_files.file_lock),

> +       .resize_wait    = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),

>  };

>

>  static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)

> --

> 2.11.0

>

 

Acked-by: Eric Dumazet <edumazet@google.com>

Fixes: 8a81252b774b ("fs/file.c: don't acquire files->file_lock in

fd_install()")