Subject: Re: [PATCH bpf-next 1/3] bpf: Support for pointers beyond pkt_end.

From: kernel test robot <[email-masked]>
Date: Thu, 22 Oct 2020 06:07:46 +0800

Hi Alexei,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]

url:    https://github.com/0day-ci/linux/commits/Alexei-Starovoitov/bpf-Pointers-beyond-packet-end/20201022-022139
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: i386-randconfig-r026-20201021 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/1aa4c81ae1dbbc3b6de7416f0384cde6cc8739b1
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Alexei-Starovoitov/bpf-Pointers-beyond-packet-end/20201022-022139
        git checkout 1aa4c81ae1dbbc3b6de7416f0384cde6cc8739b1
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email-masked]>

All warnings (new ones prefixed by >>):

   kernel/bpf/verifier.c: In function 'is_pkt_ptr_branch_taken':
>> kernel/bpf/verifier.c:7029:24: warning: variable 'pkt_end' set but not used [-Wunused-but-set-variable]
    7029 |  struct bpf_reg_state *pkt_end, *pkt;
         |                        ^~~~~~~
   In file included from include/linux/bpf_verifier.h:8,
                    from kernel/bpf/verifier.c:12:
   kernel/bpf/verifier.c: In function 'jit_subprogs':
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'unsigned int (*)(const void *, const struct bpf_insn *)' to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:10793:16: note: in expansion of macro 'BPF_CAST_CALL'
   10793 |    insn->imm = BPF_CAST_CALL(func[subprog]->bpf_func) -
         |                ^~~~~~~~~~~~~
   kernel/bpf/verifier.c: In function 'fixup_bpf_calls':
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'void * (* const)(struct bpf_map *, void *)' to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:11186:17: note: in expansion of macro 'BPF_CAST_CALL'
   11186 |     insn->imm = BPF_CAST_CALL(ops->map_lookup_elem) -
         |                 ^~~~~~~~~~~~~
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'int (* const)(struct bpf_map *, void *, void *, u64)' {aka 'int (* const)(struct bpf_map *, void *, void *, long long unsigned int)'} to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:11190:17: note: in expansion of macro 'BPF_CAST_CALL'
   11190 |     insn->imm = BPF_CAST_CALL(ops->map_update_elem) -
         |                 ^~~~~~~~~~~~~
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'int (* const)(struct bpf_map *, void *)' to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:11194:17: note: in expansion of macro 'BPF_CAST_CALL'
   11194 |     insn->imm = BPF_CAST_CALL(ops->map_delete_elem) -
         |                 ^~~~~~~~~~~~~
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'int (* const)(struct bpf_map *, void *, u64)' {aka 'int (* const)(struct bpf_map *, void *, long long unsigned int)'} to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:11198:17: note: in expansion of macro 'BPF_CAST_CALL'
   11198 |     insn->imm = BPF_CAST_CALL(ops->map_push_elem) -
         |                 ^~~~~~~~~~~~~
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'int (* const)(struct bpf_map *, void *)' to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:11202:17: note: in expansion of macro 'BPF_CAST_CALL'
   11202 |     insn->imm = BPF_CAST_CALL(ops->map_pop_elem) -
         |                 ^~~~~~~~~~~~~
   include/linux/filter.h:345:4: warning: cast between incompatible function types from 'int (* const)(struct bpf_map *, void *)' to 'u64 (*)(u64,  u64,  u64,  u64,  u64)' {aka 'long long unsigned int (*)(long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int,  long long unsigned int)'} [-Wcast-function-type]
     345 |   ((u64 (*)(u64, u64, u64, u64, u64))(x))
         |    ^
   kernel/bpf/verifier.c:11206:17: note: in expansion of macro 'BPF_CAST_CALL'
   11206 |     insn->imm = BPF_CAST_CALL(ops->map_peek_elem) -
         |                 ^~~~~~~~~~~~~

vim +/pkt_end +7029 kernel/bpf/verifier.c

  7024	
  7025	static int is_pkt_ptr_branch_taken(struct bpf_reg_state *dst_reg,
  7026					   struct bpf_reg_state *src_reg,
  7027					   u8 opcode)
  7028	{
> 7029		struct bpf_reg_state *pkt_end, *pkt;
  7030	
  7031		if (src_reg->type == PTR_TO_PACKET_END) {
  7032			pkt_end = src_reg;
  7033			pkt = dst_reg;
  7034		} else if (dst_reg->type == PTR_TO_PACKET_END) {
  7035			pkt_end = dst_reg;
  7036			pkt = src_reg;
  7037			opcode = flip_opcode(opcode);
  7038		} else {
  7039			return -1;
  7040		}
  7041	
  7042		if (pkt->range >= 0)
  7043			return -1;
  7044	
  7045		switch (opcode) {
  7046		case BPF_JLE:
  7047			/* pkt <= pkt_end */
  7048			fallthrough;
  7049		case BPF_JGT:
  7050			/* pkt > pkt_end */
  7051			if (pkt->range == BEYOND_PKT_END)
  7052				/* pkt has at last one extra byte beyond pkt_end */
  7053				return opcode == BPF_JGT;
  7054			break;
  7055		case BPF_JLT:
  7056			/* pkt < pkt_end */
  7057			fallthrough;
  7058		case BPF_JGE:
  7059			/* pkt >= pkt_end */
  7060			if (pkt->range == BEYOND_PKT_END || pkt->range == AT_PKT_END)
  7061				return opcode == BPF_JGE;
  7062			break;
  7063		}
  7064		return -1;
  7065	}
  7066	

---
0-DAY CI Kernel Test Service, Intel Corporation
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