On Tue 2023-11-14 16:26:55, Herve Codina wrote:
A refcount issue can appeared in __fwnode_link_del() due to the pr_debug() call: WARNING: CPU: 0 PID: 901 at lib/refcount.c:25 refcount_warn_saturate+0xe5/0x110 Call Trace:
<TASK> ... of_node_get+0x1e/0x30 of_fwnode_get+0x28/0x40 fwnode_full_name_string+0x34/0x90 fwnode_string+0xdb/0x140 ... vsnprintf+0x17b/0x630 ... __fwnode_link_del+0x25/0xa0 fwnode_links_purge+0x39/0xb0 of_node_release+0xd9/0x180 ...
Indeed, an fwnode (of_node) is being destroyed and so, of_node_release() is called because the of_node refcount reached 0.
From of_node_release() several function calls are done and lead to
a pr_debug() calls with %pfwf to print the fwnode full name. The issue is not present if we change %pfwf to %pfwP.
To print the full name, %pfwf iterates over the current node and its parents and obtain/drop a reference to all nodes involved.
In order to allow to print the full name (%pfwf) of a node while it is being destroyed, do not obtain/drop a reference to this current node.
Fixes: a92eb7621b9f ("lib/vsprintf: Make use of fwnode API to obtain node names and separators") Cc: stable@vger.kernel.org Signed-off-by: Herve Codina herve.codina@bootlin.com Reviewed-by: Sakari Ailus sakari.ailus@linux.intel.com Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
I have pushed the fix into printk/linux.git, branch for-6.8.
Please, let me know if you would prefer to push this into 6.7.
The "Fixes:" tag points to a pretty old commit from v5.5 so it does not look like a super urgent fix. And I always prefer when fixes spend some time in linux-next.
Best Regards, Petr