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Date:   Tue, 21 May 2019 00:16:40 -0400
From:   Kris Van Hees <kris.van.hees@oracle.com>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Kris Van Hees <kris.van.hees@oracle.com>, 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: <20190521041640.GG2422@oracle.com>
References: <201905202352.x4KNqOjS025227@userv0121.oracle.com>
 <20190520212134.7a4ee15f@oasis.local.home>
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On Mon, May 20, 2019 at 09:21:34PM -0400, Steven Rostedt wrote:
> 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.

Thanks for that advice - I will make sure to do that for future postings.

> 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.

Ah, my apologies for missing Peter in the list of Cc's.  Thank you for adding
him.  I will update my list.

	Kris

> 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