When adding a zero value to the packet pointer, the verifer
reports the following error:
R0=imm0,min_value=0,max_value=0 R1=pkt(id=0,off=0,r=4) R2=pkt_end R3=fp-12
R4=imm4,min_value=4,max_value=4 R5=pkt(id=0,off=4,r=4) R6=ctx
R7=imm0,min_value=0,max_value=0 R8=inv,min_value=0,max_value=0 R9=inv R10=fp
269: (bf) r2 = r0
270: (77) r2 >>= 3
271: (bf) r4 = r1
272: (0f) r4 += r2
addition of negative constant to packet pointer is not allowed
Signed-off-by: William Tu <u9012...@gmail.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
---
kernel/bpf/verifier.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index fb3513b..1a754e5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1397,7 +1397,7 @@ static int check_packet_ptr_add(struct bpf_verifier_env
*env,
imm = insn->imm;
add_imm:
- if (imm <= 0) {
+ if (imm < 0) {
verbose("addition of negative constant to packet
pointer is not allowed\n");
return -EACCES;
}
--
2.7.4
