Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value

From: Juergen Gross
Date: Thu May 13 2021 - 06:21:11 EST

On 13.05.21 12:16, Christophe Leroy wrote:


Le 13/05/2021 à 12:03, Juergen Gross a écrit :
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@xxxxxxxx>
---
  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;
+
      BUG_ON((prod - cons) > sizeof(intf->out));

Why keep the BUG_ON() ?

Oh, failed to delete it. Thanks for noticing.


Juergen

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