Re: [PATCH bpf-next v2 0/2] bpf: Enforce gotox targets against subprog bounds

[Anton Protopopov]

On 26/06/13 05:33PM, Nuoqi Gui wrote:
> For gotox, CFG construction models the indirect-jump target set in
> insn_aux_data->jt, but do_check() later follows targets from the runtime
> PTR_TO_INSN register's own INSN_ARRAY map. If the same gotox can be
> reached with PTR_TO_INSN values from different maps, do_check() can accept
> a target outside the subprog that CFG allowed for the gotox instruction.
> 
> On x86, that can transfer control into another subprog without a matching
> BPF call frame and crash when the program is run.

Why only on x86?

> Fix this by rejecting gotox map targets outside the current gotox subprog.
> Add a regression test covering the two-map cross-subprog case.
> 
> Validation:
> 
>   unpatched bpf-next 7bfb93e3475b with the new selftest:
>     bpf_gotox/check-cross-subprog-gotox-target: FAIL
>     cross_subprog_gotox_prog_load: actual 23 != expected -22
>     __TEST_PROGS_RC__=1
> 
>   patched bpf-next 7bfb93e3475b + this series:
>     bpf_gotox/check-cross-subprog-gotox-target: OK
>     ./test_progs -t bpf_gotox/check-cross-subprog-gotox-target
>     Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED
>     __TEST_PROGS_RC__=0

Why the second part mentions the call to ./test_progs, and the first doesn't?
Why the test result goes before the test run? Is this "Validation" section even required?

> v1 -> v2:
>   - Validate gotox runtime targets against the current subprog bounds instead
>     of scanning the CFG jump table.
>   - Fix the selftest expected error from -EACCES to -EINVAL.
> 
> v1:
>   https://lore.kernel.org/bpf/20260609-f01-02-gotox-bpf-next-v1-0-b441d63a1559@xxxxxxxxxxxxxxxxxxxxx/
> 
> Signed-off-by: Nuoqi Gui <gnq25@xxxxxxxxxxxxxxxxxxxxx>
> ---
> Nuoqi Gui (2):
>       bpf: Enforce gotox targets against subprog bounds
>       selftests/bpf: Add cross-subprog gotox target coverage
> 
>  kernel/bpf/verifier.c                              | 21 +++++++
>  tools/testing/selftests/bpf/prog_tests/bpf_gotox.c | 73 ++++++++++++++++++++++
>  2 files changed, 94 insertions(+)
> ---
> base-commit: 7bfb93e3475be9de894f1cecd3a727d3e1649b03
> change-id: 20260613-f01-02-gotox-bpf-next-v2-send-8c48c9357dde
> 
> Best regards,
> --  
> Nuoqi Gui <gnq25@xxxxxxxxxxxxxxxxxxxxx>
>