On Thu, Jul 30, 2020 at 06:09:00PM +0200, Christoph Hellwig wrote:
> __bpfilter_process_sockopt never initialized the pos variable passed to
> the pipe write. This has been mostly harmless in the past as pipes
> ignore the offset, but the switch to kernel_write no verified the
s/no/now/
> position, which can lead to a failure depending on the exact stack
> initialization patter. Initialize the variable to zero to make
s/patter/pattern/
> rw_verify_area happy.
>
> Fixes: 6955a76fbcd5 ("bpfilter: switch to kernel_write")
> Reported-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
> Reported-by: Rodrigo Madera <rodrigo.madera@xxxxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Tested-by: Rodrigo Madera <rodrigo.madera@xxxxxxxxx>
> ---
Thanks for tracking this down, Christoph! This fixes the logging issue
for me.
Tested-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
Reviewed-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
> net/bpfilter/bpfilter_kern.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> index 1905e01c3aa9a7..4494ea6056cdb8 100644
> --- a/net/bpfilter/bpfilter_kern.c
> +++ b/net/bpfilter/bpfilter_kern.c
> @@ -39,7 +39,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
> {
> struct mbox_request req;
> struct mbox_reply reply;
> - loff_t pos;
> + loff_t pos = 0;
> ssize_t n;
> int ret = -EFAULT;
>
> --
> 2.27.0
>
