From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com
[ Upstream commit f265df550a4350dce0a4d721a77c52e4b847ea40 ]
After commit ead18c23c263 ("driver core: Introduce device links reference counting"), if there is a link between the given supplier and the given consumer already, device_link_add() will refcount it and return it unconditionally. However, if the flags passed to it on the second (or any subsequent) attempt to create a device link between the same consumer-supplier pair are not compatible with the existing link's flags, that is incorrect.
First off, if the existing link is stateless and the next caller of device_link_add() for the same consumer-supplier pair wants a stateful one, or the other way around, the existing link cannot be returned, because it will not match the expected behavior, so make device_link_add() dump the stack and return NULL in that case.
Moreover, if the DL_FLAG_AUTOREMOVE_CONSUMER flag is passed to device_link_add(), its caller will expect its reference to the link to be dropped automatically on consumer driver removal, which will not happen if that flag is not set in the link's flags (and analogously for DL_FLAG_AUTOREMOVE_SUPPLIER). For this reason, make device_link_add() update the existing link's flags accordingly before returning it to the caller.
Fixes: ead18c23c263 ("driver core: Introduce device links reference counting") Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/base/core.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c index 055132f2292a..562385c47fa4 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -221,12 +221,29 @@ struct device_link *device_link_add(struct device *consumer, goto out; }
- list_for_each_entry(link, &supplier->links.consumers, s_node) - if (link->consumer == consumer) { - kref_get(&link->kref); + list_for_each_entry(link, &supplier->links.consumers, s_node) { + if (link->consumer != consumer) + continue; + + /* + * Don't return a stateless link if the caller wants a stateful + * one and vice versa. + */ + if (WARN_ON((flags & DL_FLAG_STATELESS) != (link->flags & DL_FLAG_STATELESS))) { + link = NULL; goto out; }
+ if (flags & DL_FLAG_AUTOREMOVE_CONSUMER) + link->flags |= DL_FLAG_AUTOREMOVE_CONSUMER; + + if (flags & DL_FLAG_AUTOREMOVE_SUPPLIER) + link->flags |= DL_FLAG_AUTOREMOVE_SUPPLIER; + + kref_get(&link->kref); + goto out; + } + link = kzalloc(sizeof(*link), GFP_KERNEL); if (!link) goto out;