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authorJohn Fastabend <john.fastabend@gmail.com>2020-03-24 10:38:37 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-03-25 22:51:40 -0700
commit294f2fc6da27620a506e6c050241655459ccd6bd (patch)
tree30003605c17010e065f2f92d7afcb41700eba3f2 /kernel/bpf
parent07cd263148a53ebcc911b4c96d89a72df31c8f49 (diff)
bpf: Verifer, adjust_scalar_min_max_vals to always call update_reg_bounds()
Currently, for all op verification we call __red_deduce_bounds() and __red_bound_offset() but we only call __update_reg_bounds() in bitwise ops. However, we could benefit from calling __update_reg_bounds() in BPF_ADD, BPF_SUB, and BPF_MUL cases as well. For example, a register with state 'R1_w=invP0' when we subtract from it, w1 -= 2 Before coerce we will now have an smin_value=S64_MIN, smax_value=U64_MAX and unsigned bounds umin_value=0, umax_value=U64_MAX. These will then be clamped to S32_MIN, U32_MAX values by coerce in the case of alu32 op as done in above example. However tnum will be a constant because the ALU op is done on a constant. Without update_reg_bounds() we have a scenario where tnum is a const but our unsigned bounds do not reflect this. By calling update_reg_bounds after coerce to 32bit we further refine the umin_value to U64_MAX in the alu64 case or U32_MAX in the alu32 case above. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/158507151689.15666.566796274289413203.stgit@john-Precision-5820-Tower
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 559c9afd673c..2ea2a868324e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5199,6 +5199,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
coerce_reg_to_size(dst_reg, 4);
}
+ __update_reg_bounds(dst_reg);
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
return 0;