[PATCH 4.14 068/106] tty: hvc: replace BUG_ON() with negative return value

Greg Kroah-Hartman
2021-12-06T15:17:38Z

From: Juergen Gross <jgross@suse.com>

commit e679004dec37566f658a255157d3aed9d762a2b7 upstream.

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.

Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210707091045.460-1-jgross@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/hvc/hvc_xen.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -99,7 +99,11 @@ static int __write_console(struct xencon
cons = intf->out_cons;
prod = intf->out_prod;
mb(); /* update queue values before going on */
- BUG_ON((prod - cons) > sizeof(intf->out));
+
+ if ((prod - cons) > sizeof(intf->out)) {
+ pr_err_once("xencons: Illegal ring page indices");
+ return -EINVAL;
+ }

while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
@@ -127,7 +131,10 @@ static int domU_write_console(uint32_t v
*/
while (len) {
int sent = __write_console(cons, data, len);
-
+
+ if (sent < 0)
+ return sent;
+
data += sent;
len -= sent;

@@ -151,7 +158,11 @@ static int domU_read_console(uint32_t vt
cons = intf->in_cons;
prod = intf->in_prod;
mb(); /* get pointers before reading ring */
- BUG_ON((prod - cons) > sizeof(intf->in));
+
+ if ((prod - cons) > sizeof(intf->in)) {
+ pr_err_once("xencons: Illegal ring page indices");
+ return -EINVAL;
+ }

while (cons != prod && recv < len)
buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];