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@xxxxxxxxxxxxxxx
> Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
> Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
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
