On Wed 22-11-23 14:27:07, Amir Goldstein wrote:
> In vfs code, file_start_write() is usually called after the permission
> hook in rw_verify_area(). btrfs_ioctl_encoded_write() in an exception
> to this rule.
>
> Move file_start_write() to after the rw_verify_area() check in encoded
> write to make the permission hook "start-write-safe".
>
> This is needed for fanotify "pre content" events.
>
> Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/btrfs/ioctl.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index dfe257e1845b..0a7850c4be67 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4523,29 +4523,29 @@ static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp, bool
> if (ret < 0)
> goto out_acct;
>
> - file_start_write(file);
> -
> if (iov_iter_count(&iter) == 0) {
> ret = 0;
> - goto out_end_write;
> + goto out_iov;
> }
> pos = args.offset;
> ret = rw_verify_area(WRITE, file, &pos, args.len);
> if (ret < 0)
> - goto out_end_write;
> + goto out_iov;
>
> init_sync_kiocb(&kiocb, file);
> ret = kiocb_set_rw_flags(&kiocb, 0);
> if (ret)
> - goto out_end_write;
> + goto out_iov;
> kiocb.ki_pos = pos;
>
> + file_start_write(file);
> +
> ret = btrfs_do_write_iter(&kiocb, &iter, &args);
> if (ret > 0)
> fsnotify_modify(file);
>
> -out_end_write:
> file_end_write(file);
> +out_iov:
> kfree(iov);
> out_acct:
> if (ret > 0)
> --
> 2.34.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
