linux-kernel - Re: [PATCH 5.15 33/33] selftests/bpf: Add test for reg2btf

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Date:   Fri, 1 Jul 2022 20:51:07 +0800
From:   Po-Hsu Lin <po-hsu.lin@...onical.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH 5.15 33/33] selftests/bpf: Add test for reg2btf_ids out of
 bounds access

On Fri, Jun 24, 2022 at 7:44 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Fri, Jun 24, 2022 at 06:33:57PM +0800, Po-Hsu Lin wrote:
> > On Fri, Apr 29, 2022 at 6:47 PM Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org> wrote:
> > >
> > > From: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > >
> > > commit 13c6a37d409db9abc9c0bfc6d0a2f07bf0fff60e upstream.
> > >
> > > This test tries to pass a PTR_TO_BTF_ID_OR_NULL to the release function,
> > > which would trigger a out of bounds access without the fix in commit
> > > 45ce4b4f9009 ("bpf: Fix crash due to out of bounds access into reg2btf_ids.")
> > > but after the fix, it should only index using base_type(reg->type),
> > > which should be less than __BPF_REG_TYPE_MAX, and also not permit any
> > > type flags to be set for the reg->type.
> > >
> > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
> > > Signed-off-by: Alexei Starovoitov <ast@...nel.org>
> > > Link: https://lore.kernel.org/bpf/20220220023138.2224652-1-memxor@gmail.com
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > ---
> > >  tools/testing/selftests/bpf/verifier/calls.c |   19 +++++++++++++++++++
> > >  1 file changed, 19 insertions(+)
> > >
> > > --- a/tools/testing/selftests/bpf/verifier/calls.c
> > > +++ b/tools/testing/selftests/bpf/verifier/calls.c
> > > @@ -108,6 +108,25 @@
> > >         .errstr = "R0 min value is outside of the allowed memory range",
> > >  },
> > >  {
> > > +       "calls: trigger reg2btf_ids[reg->type] for reg->type > __BPF_REG_TYPE_MAX",
> > > +       .insns = {
> > > +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
> > > +       BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),
> > > +       BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 0),
> > > +       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
> > > +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
> > > +       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, BPF_PSEUDO_KFUNC_CALL, 0, 0),
> > > +       BPF_EXIT_INSN(),
> > > +       },
> > > +       .prog_type = BPF_PROG_TYPE_SCHED_CLS,
> > > +       .result = REJECT,
> > > +       .errstr = "arg#0 pointer type STRUCT prog_test_ref_kfunc must point",
> > > +       .fixup_kfunc_btf_id = {
> > > +               { "bpf_kfunc_call_test_acquire", 3 },
> > > +               { "bpf_kfunc_call_test_release", 5 },
> > > +       },
> > > +},
> > > +{
> > >         "calls: overlapping caller/callee",
> > >         .insns = {
> > >         BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 0),
> > >
> > >
> >
> > Hello Greg,
> >
> > When I tried to build the bpf selftest from 5.15.49 source tree on a
> > Ubuntu Jammy instance running with 5.15.49-051549-generic, I got the
> > following error message:
> >
> > In file included from
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/tests.h:21,
> >                  from test_verifier.c:432:
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:124:10:
> > error: ‘struct bpf_test’ has no member named ‘fixup_kfunc_btf_id’
> >   124 |         .fixup_kfunc_btf_id = {
> >       |          ^~~~~~~~~~~~~~~~~~
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:124:9:
> > warning: braces around scalar initializer
> >   124 |         .fixup_kfunc_btf_id = {
> >       |         ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:124:9:
> > note: (near initialization for ‘tests[150].errstr_unpriv’)
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:125:17:
> > warning: braces around scalar initializer
> >   125 |                 { "bpf_kfunc_call_test_acquire", 3 },
> >       |                 ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:125:17:
> > note: (near initialization for ‘tests[150].errstr_unpriv’)
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:125:50:
> > warning: excess elements in scalar initializer
> >   125 |                 { "bpf_kfunc_call_test_acquire", 3 },
> >       |                                                  ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:125:50:
> > note: (near initialization for ‘tests[150].errstr_unpriv’)
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:126:17:
> > warning: braces around scalar initializer
> >   126 |                 { "bpf_kfunc_call_test_release", 5 },
> >       |                 ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:126:17:
> > note: (near initialization for ‘tests[150].errstr_unpriv’)
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:126:50:
> > warning: excess elements in scalar initializer
> >   126 |                 { "bpf_kfunc_call_test_release", 5 },
> >       |                                                  ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:126:50:
> > note: (near initialization for ‘tests[150].errstr_unpriv’)
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:126:17:
> > warning: excess elements in scalar initializer
> >   126 |                 { "bpf_kfunc_call_test_release", 5 },
> >       |                 ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/verifier/calls.c:126:17:
> > note: (near initialization for ‘tests[150].errstr_unpriv’)
> > make: *** [Makefile:508:
> > /home/ubuntu/linux/tools/testing/selftests/bpf/test_verifier] Error 1
> >
> > Which is introduced by this commit f59e6886c "selftests/bpf: Add test
> > for reg2btf_ids out of bounds access" on 5.15. With this commit
> > reverted, there will be another error in progs/timer_crash.c like in
> > 5.10 [1]:
> >
> > progs/timer_crash.c:8:19: error: field has incomplete type 'struct bpf_timer'
> >         struct bpf_timer timer;
> >                          ^
> > /home/ubuntu/linux/tools/testing/selftests/bpf/tools/include/bpf/bpf_helper_defs.h:39:8:
> > note: forward declaration of 'struct bpf_timer'
> > struct bpf_timer;
> >        ^
> > 1 error generated.
> >
> > Maybe commit "selftests/bpf: Add test for bpf_timer overwriting crash"
> > should be reverted on 5.15 as well.
>
> Should the test be fixed instead?
>
OK!
I will try if I can backport the fix. Otherwise will just go for the revert.
Thanks!

> I'll take patches for either, thanks.
>
> greg k-h