linux-kernel - Re: [PATCH] s390/kexec: fix memory leak of ipl report buffer

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Message-ID: <YYviwi3PVD11xcCs@osiris>
Date:   Wed, 10 Nov 2021 16:18:26 +0100
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Philipp Rudo <prudo@...hat.com>
Cc:     Baoquan He <bhe@...hat.com>, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, kexec@...ts.infradead.org,
        dyoung@...hat.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] s390/kexec: fix memory leak of ipl report buffer

On Fri, Oct 29, 2021 at 06:31:32PM +0200, Philipp Rudo wrote:
> Hi Baoquan,
> 
> On Fri, 29 Oct 2021 17:26:35 +0800
> Baoquan He <bhe@...hat.com> wrote:
> 
> > A memory leak is reported by kmemleak scanning:
...
> > The ipl report buffer is allocated via vmalloc, while has no chance to free
> > if the kexe loading is unloaded. This will cause obvious memory leak
> > when kexec/kdump kernel is reloaded, manually, or triggered, e.g by
> > memory hotplug.
> > 
> > Here, add struct kimage_arch to s390 to pass out the ipl report buffer
> > address, and introduce arch dependent function
> > arch_kimage_file_post_load_cleanup() to free it when unloaded.
> > 
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> 
> other than a missing
> 
> Fixes: 99feaa717e55 ("s390/kexec_file: Create ipl report and pass to
> next kernel")
> 
> the patch looks good to me.
> 
> Reviewed-by: Philipp Rudo <prudo@...hat.com>
...
> >  	buf.buffer = ipl_report_finish(data->report);
> >  	buf.bufsz = data->report->size;
> >  	buf.memsz = buf.bufsz;
> > +	image->arch.ipl_buf = buf.buffer;

This seems (still) to be incorrect: ipl_report_finish() may return
-ENOMEN, but there is no error checking anywhere, as far as I can
tell, which would make this:

> > +int arch_kimage_file_post_load_cleanup(struct kimage *image)
> > +{
> > +	kvfree(image->arch.ipl_buf);
> > +	image->arch.ipl_buf = NULL;
> > +
> > +	return kexec_image_post_load_cleanup_default(image);
> > +}

most likely not do what we want. That is: if this code is reached at
all in such a case. I'll check and might add a patch before this to
fix this also.