Re: [Minios-devel] [UNIKRAFT PATCH] lib/vfscore: vfscore_put_fd: do not reject fd <= 2

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

As a temporary fix this should be fine. We may get issues when we have 
proper shutdown support. Since we are anyway revisiting vfscore soon, we 
could implement those 3 basic file descriptors non-static.
Thanks!

Reviewed-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>

On 13.02.20 10:55, Hugo Lefeuvre wrote:
> Rejecting fd <= 2 is legitimate in some way, since freeing std(in|out|err)
> might lead to crash if .f_count is 1. This is because stdin, stdout and stderr
> fps are statically allocated.  However, returning -EBUSY in this case breaks
> dup2 with stdin, out, and err.  Ignoring this should be fine as long as those
> are not fdrop-ed twice.
>
> Signed-off-by: Hugo Lefeuvre <hugo.lefeuvre@xxxxxxxxx>
> ---
>   lib/vfscore/fd.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/lib/vfscore/fd.c b/lib/vfscore/fd.c
> index 6b7f5ec..684ea50 100644
> --- a/lib/vfscore/fd.c
> +++ b/lib/vfscore/fd.c
> @@ -97,9 +97,15 @@ int vfscore_put_fd(int fd)
>         unsigned long flags;
>   
>   	UK_ASSERT(fd < (int) FDTABLE_MAX_FILES);
> -       /* Currently it is not allowed to free std(in|out|err) */
> -       if (fd <= 2)
> -               return -EBUSY;
> +
> +       /* FIXME Currently it is not allowed to free std(in|out|err):
> +        * if (fd <= 2) return -EBUSY;
> +        *
> +        * However, returning -EBUSY in this case breaks dup2 with stdin, out,
> +        * err. Ignoring this should be fine as long as those are not fdrop-ed
> +        * twice, in which case the static fp would be freed, and here be
> +        * dragons.
> +        */
>   
>   	flags = ukplat_lcpu_save_irqf();
>         uk_bitmap_clear(fdtable.bitmap, fd, 1);
_______________________________________________
Minios-devel mailing list
Minios-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/minios-devel