Re: [PATCH v1] tracing/remotes: Fix leak in trace_remote_alloc_buffer() error path

[Vincent Donnefort <vdonnefort@google.com>]

On Wed, Jul 08, 2026 at 12:59:06PM -0400, Steven Rostedt wrote:
> On Wed,  8 Jul 2026 14:32:01 +0100
> Vincent Donnefort <vdonnefort@google.com> wrote:
> 
> > If page allocation fails in trace_remote_alloc_buffer(), desc->nr_cpus
> > is not yet incremented for the current CPU. As a consequence, on error,
> > half-allocated rb_desc will not be freed in trace_remote_free_buffer().
> > 
> > Include the failing CPU in desc->nr_cpus before going to the error path.
> > 
> 
> Looks like Sashiko found other issues you may want to address:
> 
>   https://sashiko.dev/#/patchset/20260708133201.295072-1-vdonnefort%40google.com

Yeah I saw it, the dreaded "This isn't a bug introduced by this patch" ...

Let me send a follow-up. After looking at the other issue, I think I want to
slightly modify this one actually!

> 
> -- Steve
> 
> > Fixes: 96e43537af54 ("tracing: Introduce trace remotes")
> > Reported-by: Sashiko <sashiko-bot@kernel.org>
> > Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
> > 
> > diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
> > index 2a6cc000ec98..62d3d431c309 100644
> > --- a/kernel/trace/trace_remote.c
> > +++ b/kernel/trace/trace_remote.c
> > @@ -1008,8 +1008,10 @@ int trace_remote_alloc_buffer(struct trace_buffer_desc *desc, size_t desc_size,
> >  
> >  		for (id = 0; id < nr_pages; id++) {
> >  			rb_desc->page_va[id] = (unsigned long)__get_free_page(GFP_KERNEL);
> > -			if (!rb_desc->page_va[id])
> > +			if (!rb_desc->page_va[id]) {
> > +				desc->nr_cpus++; /* Free this partially-allocated rb_desc */
> >  				goto err;
> > +			}
> >  
> >  			rb_desc->nr_page_va++;
> >  		}
> > 
> > base-commit: 8cdeaa50eae8dad34885515f62559ee83e7e8dda
>