On 02/03/2017 10:10 PM, William Tu wrote:
Hi Alexei,
why it is bogus? on my system, it fails without the patch applied.
--William
On Fri, Feb 3, 2017 at 12:55 PM, Alexei Starovoitov
<alexei.starovoi...@gmail.com> wrote:
On Fri, Feb 03, 2017 at 09:22:45AM -0800, William Tu wrote:
The patch fixes the case 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)
269: (bf) r2 = r0 // r2 becomes imm0
270: (77) r2 >>= 3
271: (bf) r4 = r1 // r4 becomes pkt ptr
272: (0f) r4 += r2 // r4 += 0
addition of negative constant to packet pointer is not allowed
Signed-off-by: William Tu <u9012...@gmail.com>
Signed-off-by: Mihai Budiu <mbu...@vmware.com>
[...]
{
+ "direct packet access: test14 (pkt_ptr += 0, good access)",
+ .insns = {
+ BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
+ offsetof(struct __sk_buff, data)),
+ BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1,
+ offsetof(struct __sk_buff, data_end)),
+ BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 0),
wait. the test is bogus.
please write the proper test for the feature
and check that it fails before the patch and passes afterwards.
But still same code path that is executed in verifier as BPF_K and
CONST_IMM tracked reg both share the same path under add_imm label
in check_packet_ptr_add(), no? So it becomes r2=pkt(id=0,off=0,r=0);
r0 = r2; r0 += 0 here in this test. Probably okay as well, though
there could be risk that in future both don't share the same path
for some reason. I guess you were referring to either adding tests
for BPF_K /and/ CONST_IMM reg or just the latter, right?
