From 8fa4ecd49b81ccd9d1d87f1c8b2260e218644878 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sat, 2 Dec 2023 09:56:58 -0800 Subject: bpf: enforce exact retval range on subprog/callback exit Instead of relying on potentially imprecise tnum representation of expected return value range for callbacks and subprogs, validate that smin/smax range satisfy exact expected range of return values. E.g., if callback would need to return [0, 2] range, tnum can't represent this precisely and instead will allow [0, 3] range. By checking smin/smax range, we can make sure that subprog/callback indeed returns only valid [0, 2] range. Acked-by: Eduard Zingerman Acked-by: Shung-Hsi Yu Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20231202175705.885270-5-andrii@kernel.org Signed-off-by: Alexei Starovoitov --- include/linux/bpf_verifier.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 0c0e1bccad45..3378cc753061 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -275,6 +275,11 @@ struct bpf_reference_state { int callback_ref; }; +struct bpf_retval_range { + s32 minval; + s32 maxval; +}; + /* state of the program: * type of all registers and stack info */ @@ -297,7 +302,7 @@ struct bpf_func_state { * void foo(void) { bpf_timer_set_callback(,foo); } */ u32 async_entry_cnt; - struct tnum callback_ret_range; + struct bpf_retval_range callback_ret_range; bool in_callback_fn; bool in_async_callback_fn; bool in_exception_callback_fn; -- cgit v1.2.3