linux-kernel - Re: [PATCH -fixes] bpf: resolve_btfids: Fix integer overflow when calling elf

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Date: Tue, 28 May 2024 07:12:31 +0200
From: Alexandre Ghiti <alexghiti@...osinc.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH -fixes] bpf: resolve_btfids: Fix integer overflow when
 calling elf_update()

Hi Jiri,

On Mon, May 27, 2024 at 6:00 PM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Mon, May 27, 2024 at 05:31:37PM +0200, Alexandre Ghiti wrote:
> > The following error was encoutered in [1]:
> >
> > FAILED elf_update(WRITE): no error
>
> hi,
> this fix got already in, check this patch:
>   https://patchwork.kernel.org/project/netdevbpf/patch/20240514070931.199694-1-friedrich.vock@gmx.de/

Damn, I missed this.

If possible, I think that adding the link to the bug report (or at
least the "FAILED elf_update(WRITE): no error" string) would make
sense, since it is not a "potential" overflow anymore.

Thanks,

Alex

>
> thanks,
> jirka
>
> >
> > elf_update() returns the total size of the file which here happens to be
> > a ~2.5GB vmlinux file: this size overflows the integer used to hold the
> > return value of elf_update() and is then interpreted as being negative.
> >
> > So fix this by using the correct type expected by elf_update() which is
> > off_t.
> >
> > Fixes: fbbb68de80a4 ("bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object")
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218887 [1]
> > Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
> > ---
> >  tools/bpf/resolve_btfids/main.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> > index d9520cb826b3..af393c7dee1f 100644
> > --- a/tools/bpf/resolve_btfids/main.c
> > +++ b/tools/bpf/resolve_btfids/main.c
> > @@ -728,7 +728,7 @@ static int sets_patch(struct object *obj)
> >
> >  static int symbols_patch(struct object *obj)
> >  {
> > -     int err;
> > +     off_t err;
> >
> >       if (__symbols_patch(obj, &obj->structs)  ||
> >           __symbols_patch(obj, &obj->unions)   ||
> > --
> > 2.39.2
> >