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From:   Juergen Gross <jgross@suse.com>
To:     xen-devel@lists.xenproject.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org
Cc:     Juergen Gross <jgross@suse.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>
Subject: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
Date:   Thu, 13 May 2021 12:03:02 +0200
Message-Id: <20210513100302.22027-9-jgross@suse.com>
In-Reply-To: <20210513100302.22027-1-jgross@suse.com>
References: <20210513100302.22027-1-jgross@suse.com>
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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;
+
 	BUG_ON((prod - cons) > sizeof(intf->out));
 
 	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;
 
 	while (cons != prod && recv < len)
 		buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
-- 
2.26.2