From f729a592adb6760013c3e48622a5bf256b992452 Mon Sep 17 00:00:00 2001
From: Saravana Kannan <saravanak@google.com>
Date: Wed, 29 Sep 2021 12:05:49 -0700
Subject: [PATCH] driver core: Reject pointless SYNC_STATE_ONLY device links
Git-commit: f729a592adb6760013c3e48622a5bf256b992452
Patch-mainline: v5.15-rc6
References: git-fixes stable-5.14.14
SYNC_STATE_ONLY device links intentionally allow cycles because cyclic
sync_state() dependencies are valid and necessary.
However a SYNC_STATE_ONLY device link where the consumer and the supplier
are the same device is pointless because the device link would be deleted
as soon as the device probes (because it's also the consumer) and won't
affect when the sync_state() callback is called. It's a waste of CPU cycles
and memory to create this device link. So reject any attempts to create
such a device link.
Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag")
Cc: stable <stable@vger.kernel.org>
Reported-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20210929190549.860541-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/base/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 15986cc2fe5e..249da496581a 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -687,7 +687,8 @@ struct device_link *device_link_add(struct device *consumer,
{
struct device_link *link;
- if (!consumer || !supplier || flags & ~DL_ADD_VALID_FLAGS ||
+ if (!consumer || !supplier || consumer == supplier ||
+ flags & ~DL_ADD_VALID_FLAGS ||
(flags & DL_FLAG_STATELESS && flags & DL_MANAGED_LINK_FLAGS) ||
(flags & DL_FLAG_SYNC_STATE_ONLY &&
(flags & ~DL_FLAG_INFERRED) != DL_FLAG_SYNC_STATE_ONLY) ||
--
2.26.2