Re: [PATCH 5.4 061/118] hibernate: Allow uswsusp to write to swap

[Marian Klein]

Hi Everyone
I am glad the official patch made it into 5.4 finally.
Well done everyone. Now distros should pick it up quickly , especially
ubuntu 20.04 Long Term Support.
Your most faithful fan
Marian

On Wed, 22 Apr 2020 at 11:18, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> From: Domenico Andreoli <domenico.andreoli@xxxxxxxxx>
>
> [ Upstream commit 56939e014a6c212b317414faa307029e2e80c3b9 ]
>
> It turns out that there is one use case for programs being able to
> write to swap devices, and that is the userspace hibernation code.
>
> Quick fix: disable the S_SWAPFILE check if hibernation is configured.
>
> Fixes: dc617f29dbe5 ("vfs: don't allow writes to swap files")
> Reported-by: Domenico Andreoli <domenico.andreoli@xxxxxxxxx>
> Reported-by: Marian Klein <mkleinsoft@xxxxxxxxx>
> Signed-off-by: Domenico Andreoli <domenico.andreoli@xxxxxxxxx>
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  fs/block_dev.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index d612468ee66bf..34644ce4b5025 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -34,6 +34,7 @@
>  #include <linux/task_io_accounting_ops.h>
>  #include <linux/falloc.h>
>  #include <linux/uaccess.h>
> +#include <linux/suspend.h>
>  #include "internal.h"
>
>  struct bdev_inode {
> @@ -1975,7 +1976,8 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>         if (bdev_read_only(I_BDEV(bd_inode)))
>                 return -EPERM;
>
> -       if (IS_SWAPFILE(bd_inode))
> +       /* uswsusp needs write permission to the swap */
> +       if (IS_SWAPFILE(bd_inode) && !hibernation_available())
>                 return -ETXTBSY;
>
>         if (!iov_iter_count(from))
> --
> 2.20.1
>
>
>