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Date:   Mon, 20 May 2019 21:21:34 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Kris Van Hees <kris.van.hees@oracle.com>
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
        dtrace-devel@oss.oracle.com, linux-kernel@vger.kernel.org,
        mhiramat@kernel.org, acme@kernel.org, ast@kernel.org,
        daniel@iogearbox.net, Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH 07/11] bpf: implement writable buffers in contexts
Message-ID: <20190520212134.7a4ee15f@oasis.local.home>
In-Reply-To: <201905202352.x4KNqOjS025227@userv0121.oracle.com>
References: <201905202352.x4KNqOjS025227@userv0121.oracle.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Kris,

Note, it's best to thread patches. Otherwise they get spread out in
mail boxes and hard to manage. That is, every patch should be a reply
to the 00/11 header patch.

Also, Peter Ziljstra (Cc'd) is the maintainer of perf on the kernel
side. Please include him on Ccing perf changes that are done inside the
kernel.

-- Steve


On Mon, 20 May 2019 23:52:24 +0000 (UTC)
Kris Van Hees <kris.van.hees@oracle.com> wrote:

> Currently, BPF supports writes to packet data in very specific cases.
> The implementation can be of more general use and can be extended to any
> number of writable buffers in a context.  The implementation adds two new
> register types: PTR_TO_BUFFER and PTR_TO_BUFFER_END, similar to the types
> PTR_TO_PACKET and PTR_TO_PACKET_END.  In addition, a field 'buf_id' is
> added to the reg_state structure as a way to distinguish between different
> buffers in a single context.
> 
> Buffers are specified in the context by a pair of members:
> - a pointer to the start of the buffer (type PTR_TO_BUFFER)
> - a pointer to the first byte beyond the buffer (type PTR_TO_BUFFER_END)
> 
> A context can contain multiple buffers.  Each buffer/buffer_end pair is
> identified by a unique id (buf_id).  The start-of-buffer member offset is
> usually a good unique identifier.
> 
> The semantics for using a writable buffer are the same as for packet data.
> The BPF program must contain a range test (buf + num > buf_end) to ensure
> that the verifier can verify that offsets are within the allowed range.
> 
> Whenever a helper is called that might update the content of the context
> all range information for registers that hold pointers to a buffer is
> cleared, just as it is done for packet pointers.
> 
> Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
> Reviewed-by: Nick Alcock <nick.alcock@oracle.com>
> ---
>  include/linux/bpf.h          |   3 +
>  include/linux/bpf_verifier.h |   4 +-
>  kernel/bpf/verifier.c        | 198 ++++++++++++++++++++++++-----------
>  3 files changed, 145 insertions(+), 60 deletions(-)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index e4bcb79656c4..fc3eda0192fb 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -275,6 +275,8 @@ enum bpf_reg_type {
>  	PTR_TO_TCP_SOCK,	 /* reg points to struct tcp_sock */
>  	PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */
>  	PTR_TO_TP_BUFFER,	 /* reg points to a writable raw tp's buffer */
> +	PTR_TO_BUFFER,		 /* reg points to ctx buffer */
> +	PTR_TO_BUFFER_END,	 /* reg points to ctx buffer end */
>  };
>  
>  /* The information passed from prog-specific *_is_valid_access
> @@ -283,6 +285,7 @@ enum bpf_reg_type {
>  struct bpf_insn_access_aux {
>  	enum bpf_reg_type reg_type;
>  	int ctx_field_size;
> +	u32 buf_id;
>  };
>  
>  static inline void
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 1305ccbd8fe6..3538382184f3 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -45,7 +45,7 @@ struct bpf_reg_state {
>  	/* Ordering of fields matters.  See states_equal() */
>  	enum bpf_reg_type type;
>  	union {
> -		/* valid when type == PTR_TO_PACKET */
> +		/* valid when type == PTR_TO_PACKET | PTR_TO_BUFFER */
>  		u16 range;
>  
>  		/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
> @@ -132,6 +132,8 @@ struct bpf_reg_state {
>  	 */
>  	u32 frameno;
>  	enum bpf_reg_liveness live;
> +	/* For PTR_TO_BUFFER, to identify distinct buffers in a context. */
> +	u32 buf_id;
>  };
>  
>  enum bpf_stack_slot_type {
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index f9e5536fd1af..5fba4e6f5424 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -406,6 +406,8 @@ static const char * const reg_type_str[] = {
>  	[PTR_TO_TCP_SOCK]	= "tcp_sock",
>  	[PTR_TO_TCP_SOCK_OR_NULL] = "tcp_sock_or_null",
>  	[PTR_TO_TP_BUFFER]	= "tp_buffer",
> +	[PTR_TO_BUFFER]		= "buf",
> +	[PTR_TO_BUFFER_END]	= "buf_end",
>  };
>  
>  static char slot_type_char[] = {
> @@ -467,6 +469,9 @@ static void print_verifier_state(struct bpf_verifier_env *env,
>  				verbose(env, ",off=%d", reg->off);
>  			if (type_is_pkt_pointer(t))
>  				verbose(env, ",r=%d", reg->range);
> +			else if (t == PTR_TO_BUFFER)
> +				verbose(env, ",r=%d,bid=%d", reg->range,
> +					reg->buf_id);
>  			else if (t == CONST_PTR_TO_MAP ||
>  				 t == PTR_TO_MAP_VALUE ||
>  				 t == PTR_TO_MAP_VALUE_OR_NULL)
> @@ -855,6 +860,12 @@ static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg)
>  	       reg->type == PTR_TO_PACKET_END;
>  }
>  
> +static bool reg_is_buf_pointer_any(const struct bpf_reg_state *reg)
> +{
> +	return reg_is_pkt_pointer_any(reg) ||
> +	       reg->type == PTR_TO_BUFFER || reg->type == PTR_TO_BUFFER_END;
> +}
> +
>  /* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
>  static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg,
>  				    enum bpf_reg_type which)
> @@ -1550,7 +1561,7 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
>  	return err;
>  }
>  
> -#define MAX_PACKET_OFF 0xffff
> +#define MAX_BUFFER_OFF 0xffff
>  
>  static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
>  				       const struct bpf_call_arg_meta *meta,
> @@ -1585,7 +1596,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
>  	}
>  }
>  
> -static int __check_packet_access(struct bpf_verifier_env *env, u32 regno,
> +static int __check_buffer_access(struct bpf_verifier_env *env, u32 regno,
>  				 int off, int size, bool zero_size_allowed)
>  {
>  	struct bpf_reg_state *regs = cur_regs(env);
> @@ -1593,14 +1604,15 @@ static int __check_packet_access(struct bpf_verifier_env *env, u32 regno,
>  
>  	if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
>  	    (u64)off + size > reg->range) {
> -		verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
> -			off, size, regno, reg->id, reg->off, reg->range);
> +		verbose(env, "invalid access to %s, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
> +			reg_is_pkt_pointer(reg) ? "packet" : "buffer", off,
> +			size, regno, reg->id, reg->off, reg->range);
>  		return -EACCES;
>  	}
>  	return 0;
>  }
>  
> -static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
> +static int check_buffer_access(struct bpf_verifier_env *env, u32 regno, int off,
>  			       int size, bool zero_size_allowed)
>  {
>  	struct bpf_reg_state *regs = cur_regs(env);
> @@ -1620,35 +1632,37 @@ static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
>  			regno);
>  		return -EACCES;
>  	}
> -	err = __check_packet_access(env, regno, off, size, zero_size_allowed);
> +	err = __check_buffer_access(env, regno, off, size, zero_size_allowed);
>  	if (err) {
> -		verbose(env, "R%d offset is outside of the packet\n", regno);
> +		verbose(env, "R%d offset is outside of the %s\n",
> +			regno, reg_is_pkt_pointer(reg) ? "packet" : "buffer");
>  		return err;
>  	}
>  
> -	/* __check_packet_access has made sure "off + size - 1" is within u16.
> -	 * reg->umax_value can't be bigger than MAX_PACKET_OFF which is 0xffff,
> -	 * otherwise find_good_pkt_pointers would have refused to set range info
> -	 * that __check_packet_access would have rejected this pkt access.
> -	 * Therefore, "off + reg->umax_value + size - 1" won't overflow u32.
> -	 */
> -	env->prog->aux->max_pkt_offset =
> -		max_t(u32, env->prog->aux->max_pkt_offset,
> -		      off + reg->umax_value + size - 1);
> +	if (reg_is_pkt_pointer(reg)) {
> +		/* __check_buffer_access ensures "off + size - 1" is within u16
> +		 * reg->umax_value can't be bigger than * MAX_BUFFER_OFF which
> +		 * is 0xffff, otherwise find_good_buf_pointers would have
> +		 * refused to set range info and __check_buffer_access would
> +		 * have rejected this pkt access.
> +		 * Therefore, "off + reg->umax_value + size - 1" won't overflow
> +		 * u32.
> +		 */
> +		env->prog->aux->max_pkt_offset =
> +			max_t(u32, env->prog->aux->max_pkt_offset,
> +			      off + reg->umax_value + size - 1);
> +	}
>  
>  	return err;
>  }
>  
>  /* check access to 'struct bpf_context' fields.  Supports fixed offsets only */
> -static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
> -			    enum bpf_access_type t, enum bpf_reg_type *reg_type)
> +static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx,
> +			    int off, int size, enum bpf_access_type t,
> +			    struct bpf_insn_access_aux *info)
>  {
> -	struct bpf_insn_access_aux info = {
> -		.reg_type = *reg_type,
> -	};
> -
>  	if (env->ops->is_valid_access &&
> -	    env->ops->is_valid_access(off, size, t, env->prog, &info)) {
> +	    env->ops->is_valid_access(off, size, t, env->prog, info)) {
>  		/* A non zero info.ctx_field_size indicates that this field is a
>  		 * candidate for later verifier transformation to load the whole
>  		 * field and then apply a mask when accessed with a narrower
> @@ -1656,9 +1670,7 @@ static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off,
>  		 * will only allow for whole field access and rejects any other
>  		 * type of narrower access.
>  		 */
> -		*reg_type = info.reg_type;
> -
> -		env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
> +		env->insn_aux_data[insn_idx].ctx_field_size = info->ctx_field_size;
>  		/* remember the offset of last byte accessed in ctx */
>  		if (env->prog->aux->max_ctx_offset < off + size)
>  			env->prog->aux->max_ctx_offset = off + size;
> @@ -1870,6 +1882,10 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
>  	case PTR_TO_TCP_SOCK:
>  		pointer_desc = "tcp_sock ";
>  		break;
> +	case PTR_TO_BUFFER:
> +		pointer_desc = "buffer ";
> +		strict = true;
> +		break;
>  	default:
>  		break;
>  	}
> @@ -2084,7 +2100,11 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
>  			mark_reg_unknown(env, regs, value_regno);
>  
>  	} else if (reg->type == PTR_TO_CTX) {
> -		enum bpf_reg_type reg_type = SCALAR_VALUE;
> +		struct bpf_insn_access_aux info = {
> +			.reg_type = SCALAR_VALUE,
> +			.buf_id = 0,
> +		};
> +
>  
>  		if (t == BPF_WRITE && value_regno >= 0 &&
>  		    is_pointer_value(env, value_regno)) {
> @@ -2096,21 +2116,22 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
>  		if (err < 0)
>  			return err;
>  
> -		err = check_ctx_access(env, insn_idx, off, size, t, &reg_type);
> +		err = check_ctx_access(env, insn_idx, off, size, t, &info);
>  		if (!err && t == BPF_READ && value_regno >= 0) {
>  			/* ctx access returns either a scalar, or a
>  			 * PTR_TO_PACKET[_META,_END]. In the latter
>  			 * case, we know the offset is zero.
>  			 */
> -			if (reg_type == SCALAR_VALUE) {
> +			if (info.reg_type == SCALAR_VALUE) {
>  				mark_reg_unknown(env, regs, value_regno);
>  			} else {
>  				mark_reg_known_zero(env, regs,
>  						    value_regno);
> -				if (reg_type_may_be_null(reg_type))
> +				if (reg_type_may_be_null(info.reg_type))
>  					regs[value_regno].id = ++env->id_gen;
>  			}
> -			regs[value_regno].type = reg_type;
> +			regs[value_regno].type = info.reg_type;
> +			regs[value_regno].buf_id = info.buf_id;
>  		}
>  
>  	} else if (reg->type == PTR_TO_STACK) {
> @@ -2141,7 +2162,17 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
>  				value_regno);
>  			return -EACCES;
>  		}
> -		err = check_packet_access(env, regno, off, size, false);
> +		err = check_buffer_access(env, regno, off, size, false);
> +		if (!err && t == BPF_READ && value_regno >= 0)
> +			mark_reg_unknown(env, regs, value_regno);
> +	} else if (reg->type == PTR_TO_BUFFER) {
> +		if (t == BPF_WRITE && value_regno >= 0 &&
> +		    is_pointer_value(env, value_regno)) {
> +			verbose(env, "R%d leaks addr into buffer\n",
> +				value_regno);
> +			return -EACCES;
> +		}
> +		err = check_buffer_access(env, regno, off, size, false);
>  		if (!err && t == BPF_READ && value_regno >= 0)
>  			mark_reg_unknown(env, regs, value_regno);
>  	} else if (reg->type == PTR_TO_FLOW_KEYS) {
> @@ -2382,7 +2413,7 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
>  	switch (reg->type) {
>  	case PTR_TO_PACKET:
>  	case PTR_TO_PACKET_META:
> -		return check_packet_access(env, regno, reg->off, access_size,
> +		return check_buffer_access(env, regno, reg->off, access_size,
>  					   zero_size_allowed);
>  	case PTR_TO_MAP_VALUE:
>  		if (check_map_access_type(env, regno, reg->off, access_size,
> @@ -2962,34 +2993,35 @@ static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
>  	       check_refcount_ok(fn, func_id) ? 0 : -EINVAL;
>  }
>  
> -/* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
> - * are now invalid, so turn them into unknown SCALAR_VALUE.
> +/* Packet or buffer data might have moved, any old PTR_TO_PACKET[_META,_END]
> + * and/or PTR_TO_BUFFER[_END] are now invalid, so turn them into unknown
> + * SCALAR_VALUE.
>   */
> -static void __clear_all_pkt_pointers(struct bpf_verifier_env *env,
> +static void __clear_all_buf_pointers(struct bpf_verifier_env *env,
>  				     struct bpf_func_state *state)
>  {
>  	struct bpf_reg_state *regs = state->regs, *reg;
>  	int i;
>  
>  	for (i = 0; i < MAX_BPF_REG; i++)
> -		if (reg_is_pkt_pointer_any(&regs[i]))
> +		if (reg_is_buf_pointer_any(&regs[i]))
>  			mark_reg_unknown(env, regs, i);
>  
>  	bpf_for_each_spilled_reg(i, state, reg) {
>  		if (!reg)
>  			continue;
> -		if (reg_is_pkt_pointer_any(reg))
> +		if (reg_is_buf_pointer_any(reg))
>  			__mark_reg_unknown(reg);
>  	}
>  }
>  
> -static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
> +static void clear_all_buf_pointers(struct bpf_verifier_env *env)
>  {
>  	struct bpf_verifier_state *vstate = env->cur_state;
>  	int i;
>  
>  	for (i = 0; i <= vstate->curframe; i++)
> -		__clear_all_pkt_pointers(env, vstate->frame[i]);
> +		__clear_all_buf_pointers(env, vstate->frame[i]);
>  }
>  
>  static void release_reg_references(struct bpf_verifier_env *env,
> @@ -3417,7 +3449,7 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
>  	}
>  
>  	if (changes_data)
> -		clear_all_pkt_pointers(env);
> +		clear_all_buf_pointers(env);
>  	return 0;
>  }
>  
> @@ -4349,7 +4381,7 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
>  	return 0;
>  }
>  
> -static void __find_good_pkt_pointers(struct bpf_func_state *state,
> +static void __find_good_buf_pointers(struct bpf_func_state *state,
>  				     struct bpf_reg_state *dst_reg,
>  				     enum bpf_reg_type type, u16 new_range)
>  {
> @@ -4358,7 +4390,11 @@ static void __find_good_pkt_pointers(struct bpf_func_state *state,
>  
>  	for (i = 0; i < MAX_BPF_REG; i++) {
>  		reg = &state->regs[i];
> -		if (reg->type == type && reg->id == dst_reg->id)
> +		if (reg->type != type)
> +			continue;
> +		if (type == PTR_TO_BUFFER && reg->buf_id != dst_reg->buf_id)
> +			continue;
> +		if (reg->id == dst_reg->id)
>  			/* keep the maximum range already checked */
>  			reg->range = max(reg->range, new_range);
>  	}
> @@ -4366,12 +4402,16 @@ static void __find_good_pkt_pointers(struct bpf_func_state *state,
>  	bpf_for_each_spilled_reg(i, state, reg) {
>  		if (!reg)
>  			continue;
> -		if (reg->type == type && reg->id == dst_reg->id)
> +		if (reg->type != type)
> +			continue;
> +		if (type == PTR_TO_BUFFER && reg->buf_id != dst_reg->buf_id)
> +			continue;
> +		if (reg->id == dst_reg->id)
>  			reg->range = max(reg->range, new_range);
>  	}
>  }
>  
> -static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
> +static void find_good_buf_pointers(struct bpf_verifier_state *vstate,
>  				   struct bpf_reg_state *dst_reg,
>  				   enum bpf_reg_type type,
>  				   bool range_right_open)
> @@ -4384,8 +4424,8 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
>  		/* This doesn't give us any range */
>  		return;
>  
> -	if (dst_reg->umax_value > MAX_PACKET_OFF ||
> -	    dst_reg->umax_value + dst_reg->off > MAX_PACKET_OFF)
> +	if (dst_reg->umax_value > MAX_BUFFER_OFF ||
> +	    dst_reg->umax_value + dst_reg->off > MAX_BUFFER_OFF)
>  		/* Risk of overflow.  For instance, ptr + (1<<63) may be less
>  		 * than pkt_end, but that's because it's also less than pkt.
>  		 */
> @@ -4440,10 +4480,10 @@ static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
>  	/* If our ids match, then we must have the same max_value.  And we
>  	 * don't care about the other reg's fixed offset, since if it's too big
>  	 * the range won't allow anything.
> -	 * dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16.
> +	 * dst_reg->off is known < MAX_BUFFER_OFF, therefore it fits in a u16.
>  	 */
>  	for (i = 0; i <= vstate->curframe; i++)
> -		__find_good_pkt_pointers(vstate->frame[i], dst_reg, type,
> +		__find_good_buf_pointers(vstate->frame[i], dst_reg, type,
>  					 new_range);
>  }
>  
> @@ -4934,7 +4974,7 @@ static void __mark_ptr_or_null_regs(struct bpf_func_state *state, u32 id,
>  	}
>  }
>  
> -/* The logic is similar to find_good_pkt_pointers(), both could eventually
> +/* The logic is similar to find_good_buf_pointers(), both could eventually
>   * be folded together at some point.
>   */
>  static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
> @@ -4977,14 +5017,24 @@ static bool try_match_pkt_pointers(const struct bpf_insn *insn,
>  		    (dst_reg->type == PTR_TO_PACKET_META &&
>  		     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
>  			/* pkt_data' > pkt_end, pkt_meta' > pkt_data */
> -			find_good_pkt_pointers(this_branch, dst_reg,
> +			find_good_buf_pointers(this_branch, dst_reg,
>  					       dst_reg->type, false);
>  		} else if ((dst_reg->type == PTR_TO_PACKET_END &&
>  			    src_reg->type == PTR_TO_PACKET) ||
>  			   (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
>  			    src_reg->type == PTR_TO_PACKET_META)) {
>  			/* pkt_end > pkt_data', pkt_data > pkt_meta' */
> -			find_good_pkt_pointers(other_branch, src_reg,
> +			find_good_buf_pointers(other_branch, src_reg,
> +					       src_reg->type, true);
> +		} else if (dst_reg->type == PTR_TO_BUFFER &&
> +			   src_reg->type == PTR_TO_BUFFER_END) {
> +			/* buf' > buf_end */
> +			find_good_buf_pointers(this_branch, dst_reg,
> +					       dst_reg->type, false);
> +		} else if (dst_reg->type == PTR_TO_BUFFER_END &&
> +			   src_reg->type == PTR_TO_BUFFER) {
> +			/* buf_end > buf' */
> +			find_good_buf_pointers(other_branch, src_reg,
>  					       src_reg->type, true);
>  		} else {
>  			return false;
> @@ -4996,14 +5046,24 @@ static bool try_match_pkt_pointers(const struct bpf_insn *insn,
>  		    (dst_reg->type == PTR_TO_PACKET_META &&
>  		     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
>  			/* pkt_data' < pkt_end, pkt_meta' < pkt_data */
> -			find_good_pkt_pointers(other_branch, dst_reg,
> +			find_good_buf_pointers(other_branch, dst_reg,
>  					       dst_reg->type, true);
>  		} else if ((dst_reg->type == PTR_TO_PACKET_END &&
>  			    src_reg->type == PTR_TO_PACKET) ||
>  			   (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
>  			    src_reg->type == PTR_TO_PACKET_META)) {
>  			/* pkt_end < pkt_data', pkt_data > pkt_meta' */
> -			find_good_pkt_pointers(this_branch, src_reg,
> +			find_good_buf_pointers(this_branch, src_reg,
> +					       src_reg->type, false);
> +		} else if (dst_reg->type == PTR_TO_BUFFER &&
> +			   src_reg->type == PTR_TO_BUFFER_END) {
> +			/* buf' < buf_end */
> +			find_good_buf_pointers(other_branch, dst_reg,
> +					       dst_reg->type, true);
> +		} else if (dst_reg->type == PTR_TO_BUFFER_END &&
> +			   src_reg->type == PTR_TO_BUFFER) {
> +			/* buf_end < buf' */
> +			find_good_buf_pointers(this_branch, src_reg,
>  					       src_reg->type, false);
>  		} else {
>  			return false;
> @@ -5015,14 +5075,24 @@ static bool try_match_pkt_pointers(const struct bpf_insn *insn,
>  		    (dst_reg->type == PTR_TO_PACKET_META &&
>  		     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
>  			/* pkt_data' >= pkt_end, pkt_meta' >= pkt_data */
> -			find_good_pkt_pointers(this_branch, dst_reg,
> +			find_good_buf_pointers(this_branch, dst_reg,
>  					       dst_reg->type, true);
>  		} else if ((dst_reg->type == PTR_TO_PACKET_END &&
>  			    src_reg->type == PTR_TO_PACKET) ||
>  			   (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
>  			    src_reg->type == PTR_TO_PACKET_META)) {
>  			/* pkt_end >= pkt_data', pkt_data >= pkt_meta' */
> -			find_good_pkt_pointers(other_branch, src_reg,
> +			find_good_buf_pointers(other_branch, src_reg,
> +					       src_reg->type, false);
> +		} else if (dst_reg->type == PTR_TO_BUFFER &&
> +			   src_reg->type == PTR_TO_BUFFER_END) {
> +			/* buf' >= buf_end */
> +			find_good_buf_pointers(this_branch, dst_reg,
> +					       dst_reg->type, true);
> +		} else if (dst_reg->type == PTR_TO_BUFFER_END &&
> +			   src_reg->type == PTR_TO_BUFFER) {
> +			/* buf_end >= buf' */
> +			find_good_buf_pointers(other_branch, src_reg,
>  					       src_reg->type, false);
>  		} else {
>  			return false;
> @@ -5034,15 +5104,25 @@ static bool try_match_pkt_pointers(const struct bpf_insn *insn,
>  		    (dst_reg->type == PTR_TO_PACKET_META &&
>  		     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
>  			/* pkt_data' <= pkt_end, pkt_meta' <= pkt_data */
> -			find_good_pkt_pointers(other_branch, dst_reg,
> +			find_good_buf_pointers(other_branch, dst_reg,
>  					       dst_reg->type, false);
>  		} else if ((dst_reg->type == PTR_TO_PACKET_END &&
>  			    src_reg->type == PTR_TO_PACKET) ||
>  			   (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
>  			    src_reg->type == PTR_TO_PACKET_META)) {
>  			/* pkt_end <= pkt_data', pkt_data <= pkt_meta' */
> -			find_good_pkt_pointers(this_branch, src_reg,
> +			find_good_buf_pointers(this_branch, src_reg,
>  					       src_reg->type, true);
> +		} else if (dst_reg->type == PTR_TO_BUFFER &&
> +			   src_reg->type == PTR_TO_BUFFER_END) {
> +			/* buf' <= buf_end */
> +			find_good_buf_pointers(other_branch, dst_reg,
> +					       dst_reg->type, true);
> +		} else if (dst_reg->type == PTR_TO_BUFFER_END &&
> +			   src_reg->type == PTR_TO_BUFFER) {
> +			/* buf_end <= buf' */
> +			find_good_buf_pointers(this_branch, src_reg,
> +					       src_reg->type, false);
>  		} else {
>  			return false;
>  		}
> @@ -7972,7 +8052,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
>  			 */
>  			prog->cb_access = 1;
>  			env->prog->aux->stack_depth = MAX_BPF_STACK;
> -			env->prog->aux->max_pkt_offset = MAX_PACKET_OFF;
> +			env->prog->aux->max_pkt_offset = MAX_BUFFER_OFF;
>  
>  			/* mark bpf_tail_call as different opcode to avoid
>  			 * conditional branch in the interpeter for every normal