Re: [PATCH] RDMA/restrack: Fix potential invalid address access

[Wenchao Hao]

On 2024/3/4 15:35, Leon Romanovsky wrote:
> On Mon, Mar 04, 2024 at 11:21:19AM +0800, Wenchao Hao wrote:
> > On 2024/3/3 20:57, Leon Romanovsky wrote:
> > > On Fri, Mar 01, 2024 at 05:55:15PM +0800, Wenchao Hao wrote:
> > > > struct rdma_restrack_entry's kern_name was set to KBUILD_MODNAME
> > > > in ib_create_cq(), while if the module exited but forgot del this
> > > > rdma_restrack_entry, it would cause a invalid address access in
> > > > rdma_restrack_clean() when print the owner of this rdma_restrack_entry.
> > >
> > > How is it possible to exit owner module without cleaning the resources?
> >
> > I meet this issue with one of our product who develop their owner kernel
> > modules based on ib_core, and there are terrible logic with the exit
> > code which cause resource leak.
> >
> > Of curse it's bug of module who did not clear resource when exit, but
> > I think ib_core should avoid accessing memory of other modules directly
> > to provides better stability.
> >
> > What's more, from the context of rdma_restrack_clean() when print
> > "restack: %s %s object allocated by %s is not freed ...", it seems
> > designed for the above scene where client has bug to alerts there
> > are resource leak, so we should not panic on this log print.
>
> Can you please share the kernel panic?

Sorry, there is no stack or panic info recorded. This is because
another issue of "printk". It seems printk would cause a deadlock
when printk access invalid address with our kernel.

Actually, I found this issue with ftrace/kprobe but not printk, that's
why it takes me a long time to address it.

BTW, I am not developer of rdma, after found the issue, I think it's
better to enhance, so send this patch, and the patch has been tested with
the origin scene.

> Thanks