Re: [PATCH v2 net-next] bpf: enable verifier to add 0 to packet ptr

[Daniel Borkmann]

[ please keep us Cc'ed ;) ]

On 02/03/2017 06:22 PM, 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>

Acked-by: Daniel Borkmann <dan...@iogearbox.net>

Thanks!