Re: [Minios-devel] [UNIKRAFT VFS PATCH v2 2/4] Check for NULL reference on vfscore_put_fd()

[Costin Lupu <costin.lup@xxxxxxxxx>]

Reviewed-by: Costin Lupu <costin.lupu@xxxxxxxxx>

On 6/29/19 2:12 PM, Mihai Pogonaru wrote:
> Since we can allocate a fd without assigning a
> vfscore_file we must protect against NULL pointers.
> 
> An example is the LWIP sock_fd_alloc function from sockets.c
> which firstly reserves a file descriptor by calling vfscore_alloc_fd
> and, on failure, calls vfscore_put_fd. But the failure might occur
> before associating an actual vfscore_file with the fd.
> 
> Signed-off-by: Mihai Pogonaru <pogonarumihai@xxxxxxxxx>
> ---
>  lib/vfscore/fd.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/vfscore/fd.c b/lib/vfscore/fd.c
> index f8b24020..01025a46 100644
> --- a/lib/vfscore/fd.c
> +++ b/lib/vfscore/fd.c
> @@ -88,7 +88,12 @@ void vfscore_put_fd(int fd)
>       fdtable.files[fd] = NULL;
>       ukplat_lcpu_restore_irqf(flags);
>  
> -     fdrop(fp);
> +     /*
> +      * Since we can alloc a fd without assigning a
> +      * vfsfile we must protect against NULL ptr
> +      */
> +     if (fp)
> +             fdrop(fp);
>  }
>  
>  int vfscore_install_fd(int fd, struct vfscore_file *file)
> 

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