From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Juergen Gross <jgross@suse.com>
Cc: xen-devel@lists.xenproject.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org, Jiri Slaby <jirislaby@kernel.org>
Subject: Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
Date: Thu, 13 May 2021 12:25:44 +0200 [thread overview]
Message-ID: <YJz+qK8snI64/TKh@kroah.com> (raw)
In-Reply-To: <20210513100302.22027-9-jgross@suse.com>
On Thu, May 13, 2021 at 12:03:02PM +0200, Juergen Gross wrote:
> Xen frontends shouldn't BUG() in case of illegal data received from
> their backends. So replace the BUG_ON()s when reading illegal data from
> the ring page with negative return values.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
> drivers/tty/hvc/hvc_xen.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> index 92c9a476defc..30d7ffb1e04c 100644
> --- a/drivers/tty/hvc/hvc_xen.c
> +++ b/drivers/tty/hvc/hvc_xen.c
> @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons,
> cons = intf->out_cons;
> prod = intf->out_prod;
> mb(); /* update queue values before going on */
> +
> + if (WARN_ONCE((prod - cons) > sizeof(intf->out),
> + "Illegal ring page indices"))
> + return -EINVAL;
How nice, you just rebooted on panic-on-warn systems :(
> +
> BUG_ON((prod - cons) > sizeof(intf->out));
Why keep this line?
Please just fix this up properly, if userspace can trigger this, then
both the WARN_ON() and BUG_ON() are not correct and need to be correctly
handled.
>
> while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
> @@ -114,7 +119,10 @@ static int domU_write_console(uint32_t vtermno, const char *data, int len)
> */
> while (len) {
> int sent = __write_console(cons, data, len);
> -
> +
> + if (sent < 0)
> + return sent;
> +
> data += sent;
> len -= sent;
>
> @@ -138,7 +146,10 @@ static int domU_read_console(uint32_t vtermno, char *buf, int len)
> cons = intf->in_cons;
> prod = intf->in_prod;
> mb(); /* get pointers before reading ring */
> - BUG_ON((prod - cons) > sizeof(intf->in));
> +
> + if (WARN_ONCE((prod - cons) > sizeof(intf->in),
> + "Illegal ring page indices"))
> + return -EINVAL;
Same here, you still just paniced a machine :(
thanks,
greg k-h
next prev parent reply other threads:[~2021-05-13 10:25 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 10:02 [PATCH 0/8] xen: harden frontends against malicious backends Juergen Gross
2021-05-13 10:02 ` [PATCH 1/8] xen: sync include/xen/interface/io/ring.h with Xen's newest version Juergen Gross
2021-05-13 10:02 ` [PATCH 2/8] xen/blkfront: read response from backend only once Juergen Gross
2021-05-17 13:50 ` Jan Beulich
2021-05-13 10:02 ` [PATCH 3/8] xen/blkfront: don't take local copy of a request from the ring page Juergen Gross
2021-05-17 14:01 ` Jan Beulich
2021-05-17 14:11 ` Juergen Gross
2021-05-13 10:02 ` [PATCH 4/8] xen/blkfront: don't trust the backend response data blindly Juergen Gross
2021-05-17 14:11 ` Jan Beulich
2021-05-17 14:23 ` Juergen Gross
2021-05-17 15:12 ` Jan Beulich
2021-05-17 15:22 ` Juergen Gross
2021-05-17 15:33 ` Jan Beulich
2021-07-08 5:47 ` Juergen Gross
2021-07-08 6:37 ` Jan Beulich
2021-07-08 6:40 ` Juergen Gross
2021-07-08 6:52 ` Jan Beulich
2021-07-08 6:56 ` Juergen Gross
2021-05-13 10:02 ` [PATCH 5/8] xen/netfront: read response from backend only once Juergen Gross
2021-05-17 14:20 ` Jan Beulich
2021-05-17 14:24 ` Juergen Gross
2021-05-13 10:03 ` [PATCH 6/8] xen/netfront: don't read data from request on the ring page Juergen Gross
2021-05-17 15:08 ` Jan Beulich
2021-05-13 10:03 ` [PATCH 7/8] xen/netfront: don't trust the backend response data blindly Juergen Gross
2021-05-17 15:31 ` Jan Beulich
2021-05-13 10:03 ` [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value Juergen Gross
2021-05-13 10:16 ` Christophe Leroy
2021-05-13 10:20 ` Juergen Gross
2021-05-13 10:25 ` Greg Kroah-Hartman [this message]
2021-05-13 10:35 ` Juergen Gross
2021-05-21 10:43 ` [PATCH 0/8] xen: harden frontends against malicious backends Marek Marczykowski-Górecki
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