Re: [PATCH] interconnect: debugfs: fix devm_kstrdup and kfree mismatch

[Markus Elfring <Markus.Elfring@web.de>]

> debugfs_write_file_str() uses standard kfree() to release old strings.

Why would such information matter here?


> Initializing src_node and dst_node with devm_kstrdup() creates a memory
> management mismatch. If a user writes to these debugfs nodes, the
> devm-allocated memory is freed via kfree(), leaving a dangling pointer
> in the device resource list that can lead to a double free.

Would an other description approach be clearer for involved dependencies?


> Fix this by using standard kstrdup() instead.

Interesting …

https://elixir.bootlin.com/linux/v7.0-rc4/source/drivers/interconnect/debugfs-client.c#L139-L169


>                                               Since the interconnect
> subsystem is strictly built-in and cannot be unloaded as a module, there
> is no exit path requiring manual cleanup of these strings.

Should string lifetimes be reconsidered for the mentioned function implementation?


>                                                            The error
> handling path is also simplified by taking advantage of the fact that
> kfree(NULL) is a safe no-op.

I tend to interpret source code simplifications in other directions.


See also once more:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/stable-kernel-rules.rst?h=v7.0-rc4#n34

Regards,
Markus