linux-kernel - [PATCH v2 7/8] virt: vbox: Log unknown ioctl requests as error

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Message-Id: <20200623142752.4331-8-hdegoede@redhat.com>
Date:   Tue, 23 Jun 2020 16:27:51 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Hans de Goede <hdegoede@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 7/8] virt: vbox: Log unknown ioctl requests as error

Every now and then upstream adds new ioctls without notifying us,
log unknown ioctl requests as an error to catch these.

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
---
Changes in v2:
- Rate-limit the error logging to avoid userspace potentially DOS-ing the log
---
 drivers/virt/vboxguest/vboxguest_core.c  | 2 +-
 drivers/virt/vboxguest/vboxguest_utils.c | 1 +
 include/linux/vbox_utils.h               | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/virt/vboxguest/vboxguest_core.c b/drivers/virt/vboxguest/vboxguest_core.c
index ffd76b949276..c5dfcd42fd07 100644
--- a/drivers/virt/vboxguest/vboxguest_core.c
+++ b/drivers/virt/vboxguest/vboxguest_core.c
@@ -1739,7 +1739,7 @@ int vbg_core_ioctl(struct vbg_session *session, unsigned int req, void *data)
 		return vbg_ioctl_log(data);
 	}
 
-	vbg_debug("VGDrvCommonIoCtl: Unknown req %#08x\n", req);
+	vbg_err_ratelimited("Userspace made an unknown ioctl req %#08x\n", req);
 	return -ENOTTY;
 }
 
diff --git a/drivers/virt/vboxguest/vboxguest_utils.c b/drivers/virt/vboxguest/vboxguest_utils.c
index 7396187ee32a..ea05af41ec69 100644
--- a/drivers/virt/vboxguest/vboxguest_utils.c
+++ b/drivers/virt/vboxguest/vboxguest_utils.c
@@ -59,6 +59,7 @@ EXPORT_SYMBOL(name)
 VBG_LOG(vbg_info, pr_info);
 VBG_LOG(vbg_warn, pr_warn);
 VBG_LOG(vbg_err, pr_err);
+VBG_LOG(vbg_err_ratelimited, pr_err_ratelimited);
 #if defined(DEBUG) && !defined(CONFIG_DYNAMIC_DEBUG)
 VBG_LOG(vbg_debug, pr_debug);
 #endif
diff --git a/include/linux/vbox_utils.h b/include/linux/vbox_utils.h
index ff56c443180c..db8a7d118093 100644
--- a/include/linux/vbox_utils.h
+++ b/include/linux/vbox_utils.h
@@ -16,6 +16,7 @@ struct vbg_dev;
 __printf(1, 2) void vbg_info(const char *fmt, ...);
 __printf(1, 2) void vbg_warn(const char *fmt, ...);
 __printf(1, 2) void vbg_err(const char *fmt, ...);
+__printf(1, 2) void vbg_err_ratelimited(const char *fmt, ...);
 
 /* Only use backdoor logging for non-dynamic debug builds */
 #if defined(DEBUG) && !defined(CONFIG_DYNAMIC_DEBUG)
-- 
2.26.2