[PATCH] Fix a bug in ebpf verifier

[lonial con <kongln9170@gmail.com>]

In find_equal_scalars(), it should not copy the reg->subreg_def, otherwise a bug will occur when the program flag has BPF_F_TEST_RND_HI32.

Reported-by: Lonial Con <kongln9170@gmail.com>
Signed-off-by: Lonial Con <kongln9170@gmail.com>
---
 kernel/bpf/verifier.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d852009..1e01b7f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -15101,7 +15101,9 @@ static void find_equal_scalars(struct bpf_verifier_state *vstate,
 			continue;
 		if ((!(reg->id & BPF_ADD_CONST) && !(known_reg->id & BPF_ADD_CONST)) ||
 		    reg->off == known_reg->off) {
+			s32 subreg_def = reg->subreg_def;
 			copy_register_state(reg, known_reg);
+			reg->subreg_def = subreg_def;
 		} else {
 			s32 saved_off = reg->off;
 
@@ -15109,7 +15111,9 @@ static void find_equal_scalars(struct bpf_verifier_state *vstate,
 			__mark_reg_known(&fake_reg, (s32)reg->off - (s32)known_reg->off);
 
 			/* reg = known_reg; reg += delta */
+			s32 subreg_def = reg->subreg_def;
 			copy_register_state(reg, known_reg);
+			reg->subreg_def = subreg_def;
 			/*
 			 * Must preserve off, id and add_const flag,
 			 * otherwise another find_equal_scalars() will be incorrect.
-- 
2.7.4