From be8ef91d61663bfcc79f5c0eb33f9a26ab74de73 Mon Sep 17 00:00:00 2001 From: Saravana Kannan Date: Wed, 29 Sep 2021 12:05:49 -0700 Subject: [PATCH] driver core: Reject pointless SYNC_STATE_ONLY device links commit f729a592adb6760013c3e48622a5bf256b992452 upstream. 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 Reported-by: Ulf Hansson Reviewed-by: Rafael J. Wysocki Reviewed-by: Ulf Hansson Signed-off-by: Saravana Kannan Link: https://lore.kernel.org/r/20210929190549.860541-1-saravanak@google.com Signed-off-by: Greg Kroah-Hartman --- 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 a364fe565007..2bc4db5ffe44 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -549,7 +549,8 @@ 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_SYNC_STATE_ONLY) || -- 2.34.1