linux-kernel - Re: kmemleak panic

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Date:   Mon, 21 Jan 2019 09:42:07 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Marc Gonzalez <marc.w.gonzalez@...e.fr>,
        Frank Rowand <frowand.list@...il.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Oscar Salvador <osalvador@...e.de>,
        Wei Yang <richard.weiyang@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sri Krishna chowdary <schowdary@...dia.com>,
        Qian Cai <cai@....pw>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: kmemleak panic

+Mike Rapoport

On Mon, Jan 21, 2019 at 8:37 AM Catalin Marinas <catalin.marinas@....com> wrote:
>
> On Mon, Jan 21, 2019 at 07:35:11AM -0600, Rob Herring wrote:
> > On Mon, Jan 21, 2019 at 6:19 AM Robin Murphy <robin.murphy@....com> wrote:
> > >
> > > On 21/01/2019 11:57, Marc Gonzalez wrote:
> > > [...]
> > > > # echo dump=0xffffffc021e00000 > /sys/kernel/debug/kmemleak
> > > > kmemleak: Object 0xffffffc021e00000 (size 2097152):
> > > > kmemleak:   comm "swapper/0", pid 0, jiffies 4294892296
> > > > kmemleak:   min_count = 0
> > > > kmemleak:   count = 0
> > > > kmemleak:   flags = 0x1
> > > > kmemleak:   checksum = 0
> > > > kmemleak:   backtrace:
> > > >       kmemleak_alloc_phys+0x48/0x60
> > > >       memblock_alloc_range_nid+0x8c/0xa4
> > > >       memblock_alloc_base_nid+0x4c/0x60
> > > >       __memblock_alloc_base+0x3c/0x4c
> > > >       early_init_dt_alloc_reserved_memory_arch+0x54/0xa4
> > > >       fdt_init_reserved_mem+0x308/0x3ec
> > > >       early_init_fdt_scan_reserved_mem+0x88/0xb0
> > > >       arm64_memblock_init+0x1dc/0x254
> > > >       setup_arch+0x1c8/0x4ec
> > > >       start_kernel+0x84/0x44c
> > > >       0xffffffffffffffff
> > >
> > > OK, so via the __va(phys) call in kmemleak_alloc_phys(), you end up with
> > > the linear map address of a no-map reservation, which unsurprisingly
> > > turns out not to be mapped. Is there a way to tell kmemleak that it
> > > can't scan within a particular object?
> >
> > There was this patch posted[1]. I never got a reply, so it hasn't been applied.
> >
> > https://patchwork.ozlabs.org/patch/995367/
>
> Thanks Rob, I wasn't aware of this patch (or I just missed it at the
> time).
>
> I wonder whether kmemleak should simply remove ranges passed to
> memblock_remove(), or at least mark them as no-scan.

Seems reasonable to me, but of course that impacts a lot of other
cases. Maybe Mike R has some thoughts?

Rob