Sorry about all the noise, please disregard this one.
On Sat, Jul 25, 2020 at 7:04 PM Pascal Bouchareine <kalou@xxxxxxx> wrote:
>
> One intended usage is to allow processes to self-document sockets
> for netstat and friends to report
>
> Signed-off-by: Pascal Bouchareine <kalou@xxxxxxx>
> ---
> Documentation/filesystems/proc.rst | 3 +++
> fs/fcntl.c | 19 +++++++++++++++++++
> fs/file_table.c | 2 ++
> fs/proc/fd.c | 5 +++++
> include/linux/fs.h | 3 +++
> include/uapi/linux/fcntl.h | 5 +++++
> 6 files changed, 37 insertions(+)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 996f3cfe7030..ae8045650836 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -1918,6 +1918,9 @@ A typical output is::
> flags: 0100002
> mnt_id: 19
>
> +An optional 'desc' is set if the process documented its usage of
> +the file via the fcntl command F_SET_DESCRIPTION.
> +
> All locks associated with a file descriptor are shown in its fdinfo too::
>
> lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 2e4c0fa2074b..c1ef724a906e 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -319,6 +319,22 @@ static long fcntl_rw_hint(struct file *file, unsigned int cmd,
> }
> }
>
> +static long fcntl_set_description(struct file *file, char __user *desc)
> +{
> + char *d;
> +
> + d = strndup_user(desc, MAX_FILE_DESC_SIZE);
> + if (IS_ERR(d))
> + return PTR_ERR(d);
> +
> + spin_lock(&file->f_lock);
> + kfree(file->f_description);
> + file->f_description = d;
> + spin_unlock(&file->f_lock);
> +
> + return 0;
> +}
> +
> static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
> struct file *filp)
> {
> @@ -426,6 +442,9 @@ static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
> case F_SET_FILE_RW_HINT:
> err = fcntl_rw_hint(filp, cmd, arg);
> break;
> + case F_SET_DESCRIPTION:
> + err = fcntl_set_description(filp, argp);
> + break;
> default:
> break;
> }
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 656647f9575a..6673a48d2ea1 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -272,6 +272,8 @@ static void __fput(struct file *file)
> eventpoll_release(file);
> locks_remove_file(file);
>
> + kfree(file->f_description);
> +
> ima_file_free(file);
> if (unlikely(file->f_flags & FASYNC)) {
> if (file->f_op->fasync)
> diff --git a/fs/proc/fd.c b/fs/proc/fd.c
> index 81882a13212d..60b3ff971b2b 100644
> --- a/fs/proc/fd.c
> +++ b/fs/proc/fd.c
> @@ -57,6 +57,11 @@ static int seq_show(struct seq_file *m, void *v)
> (long long)file->f_pos, f_flags,
> real_mount(file->f_path.mnt)->mnt_id);
>
> + spin_lock(&file->f_lock);
> + if (file->f_description)
> + seq_printf(m, "desc:\t%s\n", file->f_description);
> + spin_unlock(&file->f_lock);
> +
> show_fd_locks(m, file, files);
> if (seq_has_overflowed(m))
> goto out;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index f5abba86107d..09717bfa4e3b 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -980,6 +980,9 @@ struct file {
> struct address_space *f_mapping;
> errseq_t f_wb_err;
> errseq_t f_sb_err; /* for syncfs */
> +
> +#define MAX_FILE_DESC_SIZE 256
> + char *f_description;
> } __randomize_layout
> __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */
>
> diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
> index 2f86b2ad6d7e..f86ff6dc45c7 100644
> --- a/include/uapi/linux/fcntl.h
> +++ b/include/uapi/linux/fcntl.h
> @@ -55,6 +55,11 @@
> #define F_GET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 13)
> #define F_SET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 14)
>
> +/*
> + * Set file description
> + */
> +#define F_SET_DESCRIPTION (F_LINUX_SPECIFIC_BASE + 15)
> +
> /*
> * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be
> * used to clear any hints previously set.
> --
> 2.25.1
>
