/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
+ * Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
FRAME_PTR, /* reg == frame_pointer */
PTR_TO_STACK, /* reg == frame_pointer + imm */
CONST_IMM, /* constant integer value */
+
+ /* PTR_TO_PACKET represents:
+ * skb->data
+ * skb->data + imm
+ * skb->data + (u16) var
+ * skb->data + (u16) var + imm
+ * if (range > 0) then [ptr, ptr + range - off) is safe to access
+ * if (id > 0) means that some 'var' was added
+ * if (off > 0) menas that 'imm' was added
+ */
+ PTR_TO_PACKET,
+ PTR_TO_PACKET_END, /* skb->data + headlen */
};
struct reg_state {
enum bpf_reg_type type;
union {
- /* valid when type == CONST_IMM | PTR_TO_STACK */
- long imm;
+ /* valid when type == CONST_IMM | PTR_TO_STACK | UNKNOWN_VALUE */
+ s64 imm;
+
+ /* valid when type == PTR_TO_PACKET* */
+ struct {
+ u32 id;
+ u16 off;
+ u16 range;
+ };
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
* PTR_TO_MAP_VALUE_OR_NULL
[FRAME_PTR] = "fp",
[PTR_TO_STACK] = "fp",
[CONST_IMM] = "imm",
+ [PTR_TO_PACKET] = "pkt",
+ [PTR_TO_PACKET_END] = "pkt_end",
};
static void print_verifier_state(struct verifier_state *state)
continue;
verbose(" R%d=%s", i, reg_type_str[t]);
if (t == CONST_IMM || t == PTR_TO_STACK)
- verbose("%ld", reg->imm);
+ verbose("%lld", reg->imm);
+ else if (t == PTR_TO_PACKET)
+ verbose("(id=%d,off=%d,r=%d)",
+ reg->id, reg->off, reg->range);
+ else if (t == UNKNOWN_VALUE && reg->imm)
+ verbose("%lld", reg->imm);
else if (t == CONST_PTR_TO_MAP || t == PTR_TO_MAP_VALUE ||
t == PTR_TO_MAP_VALUE_OR_NULL)
verbose("(ks=%d,vs=%d)",
case PTR_TO_MAP_VALUE_OR_NULL:
case PTR_TO_STACK:
case PTR_TO_CTX:
+ case PTR_TO_PACKET:
+ case PTR_TO_PACKET_END:
case FRAME_PTR:
case CONST_PTR_TO_MAP:
return true;
return 0;
}
+#define MAX_PACKET_OFF 0xffff
+
+static int check_packet_access(struct verifier_env *env, u32 regno, int off,
+ int size)
+{
+ struct reg_state *regs = env->cur_state.regs;
+ struct reg_state *reg = ®s[regno];
+ int linear_size = (int) reg->range - (int) reg->off;
+
+ if (linear_size < 0 || linear_size >= MAX_PACKET_OFF) {
+ verbose("verifier bug\n");
+ return -EFAULT;
+ }
+ if (off < 0 || off + size > linear_size) {
+ verbose("invalid access to packet, off=%d size=%d, allowed=%d\n",
+ off, size, linear_size);
+ return -EACCES;
+ }
+ return 0;
+}
+
/* check access to 'struct bpf_context' fields */
static int check_ctx_access(struct verifier_env *env, int off, int size,
enum bpf_access_type t)
}
}
+static int check_ptr_alignment(struct verifier_env *env, struct reg_state *reg,
+ int off, int size)
+{
+ if (reg->type != PTR_TO_PACKET) {
+ if (off % size != 0) {
+ verbose("misaligned access off %d size %d\n", off, size);
+ return -EACCES;
+ } else {
+ return 0;
+ }
+ }
+
+ switch (env->prog->type) {
+ case BPF_PROG_TYPE_SCHED_CLS:
+ case BPF_PROG_TYPE_SCHED_ACT:
+ break;
+ default:
+ verbose("verifier is misconfigured\n");
+ return -EACCES;
+ }
+
+ if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+ /* misaligned access to packet is ok on x86,arm,arm64 */
+ return 0;
+
+ if (reg->id && size != 1) {
+ verbose("Unknown packet alignment. Only byte-sized access allowed\n");
+ return -EACCES;
+ }
+
+ /* skb->data is NET_IP_ALIGN-ed */
+ if ((NET_IP_ALIGN + reg->off + off) % size != 0) {
+ verbose("misaligned packet access off %d+%d+%d size %d\n",
+ NET_IP_ALIGN, reg->off, off, size);
+ return -EACCES;
+ }
+ return 0;
+}
+
/* check whether memory at (regno + off) is accessible for t = (read | write)
* if t==write, value_regno is a register which value is stored into memory
* if t==read, value_regno is a register which will receive the value from memory
if (size < 0)
return size;
- if (off % size != 0) {
- verbose("misaligned access off %d size %d\n", off, size);
- return -EACCES;
- }
+ err = check_ptr_alignment(env, reg, off, size);
+ if (err)
+ return err;
if (reg->type == PTR_TO_MAP_VALUE) {
if (t == BPF_WRITE && value_regno >= 0 &&
return -EACCES;
}
err = check_ctx_access(env, off, size, t);
- if (!err && t == BPF_READ && value_regno >= 0)
+ if (!err && t == BPF_READ && value_regno >= 0) {
mark_reg_unknown_value(state->regs, value_regno);
+ if (off == offsetof(struct __sk_buff, data) &&
+ env->allow_ptr_leaks)
+ /* note that reg.[id|off|range] == 0 */
+ state->regs[value_regno].type = PTR_TO_PACKET;
+ else if (off == offsetof(struct __sk_buff, data_end) &&
+ env->allow_ptr_leaks)
+ state->regs[value_regno].type = PTR_TO_PACKET_END;
+ }
} else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) {
if (off >= 0 || off < -MAX_BPF_STACK) {
} else {
err = check_stack_read(state, off, size, value_regno);
}
+ } else if (state->regs[regno].type == PTR_TO_PACKET) {
+ if (t == BPF_WRITE) {
+ verbose("cannot write into packet\n");
+ return -EACCES;
+ }
+ err = check_packet_access(env, regno, off, size);
+ if (!err && t == BPF_READ && value_regno >= 0)
+ mark_reg_unknown_value(state->regs, value_regno);
} else {
verbose("R%d invalid mem access '%s'\n",
regno, reg_type_str[reg->type]);
return -EACCES;
}
+
+ if (!err && size <= 2 && value_regno >= 0 && env->allow_ptr_leaks &&
+ state->regs[value_regno].type == UNKNOWN_VALUE) {
+ /* 1 or 2 byte load zero-extends, determine the number of
+ * zero upper bits. Not doing it fo 4 byte load, since
+ * such values cannot be added to ptr_to_packet anyway.
+ */
+ state->regs[value_regno].imm = 64 - size * 8;
+ }
return err;
}
return count > 1 ? -EINVAL : 0;
}
+static void clear_all_pkt_pointers(struct verifier_env *env)
+{
+ struct verifier_state *state = &env->cur_state;
+ struct reg_state *regs = state->regs, *reg;
+ int i;
+
+ for (i = 0; i < MAX_BPF_REG; i++)
+ if (regs[i].type == PTR_TO_PACKET ||
+ regs[i].type == PTR_TO_PACKET_END)
+ mark_reg_unknown_value(regs, i);
+
+ for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
+ if (state->stack_slot_type[i] != STACK_SPILL)
+ continue;
+ reg = &state->spilled_regs[i / BPF_REG_SIZE];
+ if (reg->type != PTR_TO_PACKET &&
+ reg->type != PTR_TO_PACKET_END)
+ continue;
+ reg->type = UNKNOWN_VALUE;
+ reg->imm = 0;
+ }
+}
+
static int check_call(struct verifier_env *env, int func_id)
{
struct verifier_state *state = &env->cur_state;
struct reg_state *regs = state->regs;
struct reg_state *reg;
struct bpf_call_arg_meta meta;
+ bool changes_data;
int i, err;
/* find function prototype */
return -EINVAL;
}
+ changes_data = bpf_helper_changes_skb_data(fn->func);
+
memset(&meta, 0, sizeof(meta));
/* We only support one arg being in raw mode at the moment, which
if (err)
return err;
+ if (changes_data)
+ clear_all_pkt_pointers(env);
+ return 0;
+}
+
+static int check_packet_ptr_add(struct verifier_env *env, struct bpf_insn *insn)
+{
+ struct reg_state *regs = env->cur_state.regs;
+ struct reg_state *dst_reg = ®s[insn->dst_reg];
+ struct reg_state *src_reg = ®s[insn->src_reg];
+ s32 imm;
+
+ if (BPF_SRC(insn->code) == BPF_K) {
+ /* pkt_ptr += imm */
+ imm = insn->imm;
+
+add_imm:
+ if (imm <= 0) {
+ verbose("addition of negative constant to packet pointer is not allowed\n");
+ return -EACCES;
+ }
+ if (imm >= MAX_PACKET_OFF ||
+ imm + dst_reg->off >= MAX_PACKET_OFF) {
+ verbose("constant %d is too large to add to packet pointer\n",
+ imm);
+ return -EACCES;
+ }
+ /* a constant was added to pkt_ptr.
+ * Remember it while keeping the same 'id'
+ */
+ dst_reg->off += imm;
+ } else {
+ if (src_reg->type == CONST_IMM) {
+ /* pkt_ptr += reg where reg is known constant */
+ imm = src_reg->imm;
+ goto add_imm;
+ }
+ /* disallow pkt_ptr += reg
+ * if reg is not uknown_value with guaranteed zero upper bits
+ * otherwise pkt_ptr may overflow and addition will become
+ * subtraction which is not allowed
+ */
+ if (src_reg->type != UNKNOWN_VALUE) {
+ verbose("cannot add '%s' to ptr_to_packet\n",
+ reg_type_str[src_reg->type]);
+ return -EACCES;
+ }
+ if (src_reg->imm < 48) {
+ verbose("cannot add integer value with %lld upper zero bits to ptr_to_packet\n",
+ src_reg->imm);
+ return -EACCES;
+ }
+ /* dst_reg stays as pkt_ptr type and since some positive
+ * integer value was added to the pointer, increment its 'id'
+ */
+ dst_reg->id++;
+
+ /* something was added to pkt_ptr, set range and off to zero */
+ dst_reg->off = 0;
+ dst_reg->range = 0;
+ }
+ return 0;
+}
+
+static int evaluate_reg_alu(struct verifier_env *env, struct bpf_insn *insn)
+{
+ struct reg_state *regs = env->cur_state.regs;
+ struct reg_state *dst_reg = ®s[insn->dst_reg];
+ u8 opcode = BPF_OP(insn->code);
+ s64 imm_log2;
+
+ /* for type == UNKNOWN_VALUE:
+ * imm > 0 -> number of zero upper bits
+ * imm == 0 -> don't track which is the same as all bits can be non-zero
+ */
+
+ if (BPF_SRC(insn->code) == BPF_X) {
+ struct reg_state *src_reg = ®s[insn->src_reg];
+
+ if (src_reg->type == UNKNOWN_VALUE && src_reg->imm > 0 &&
+ dst_reg->imm && opcode == BPF_ADD) {
+ /* dreg += sreg
+ * where both have zero upper bits. Adding them
+ * can only result making one more bit non-zero
+ * in the larger value.
+ * Ex. 0xffff (imm=48) + 1 (imm=63) = 0x10000 (imm=47)
+ * 0xffff (imm=48) + 0xffff = 0x1fffe (imm=47)
+ */
+ dst_reg->imm = min(dst_reg->imm, src_reg->imm);
+ dst_reg->imm--;
+ return 0;
+ }
+ if (src_reg->type == CONST_IMM && src_reg->imm > 0 &&
+ dst_reg->imm && opcode == BPF_ADD) {
+ /* dreg += sreg
+ * where dreg has zero upper bits and sreg is const.
+ * Adding them can only result making one more bit
+ * non-zero in the larger value.
+ */
+ imm_log2 = __ilog2_u64((long long)src_reg->imm);
+ dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
+ dst_reg->imm--;
+ return 0;
+ }
+ /* all other cases non supported yet, just mark dst_reg */
+ dst_reg->imm = 0;
+ return 0;
+ }
+
+ /* sign extend 32-bit imm into 64-bit to make sure that
+ * negative values occupy bit 63. Note ilog2() would have
+ * been incorrect, since sizeof(insn->imm) == 4
+ */
+ imm_log2 = __ilog2_u64((long long)insn->imm);
+
+ if (dst_reg->imm && opcode == BPF_LSH) {
+ /* reg <<= imm
+ * if reg was a result of 2 byte load, then its imm == 48
+ * which means that upper 48 bits are zero and shifting this reg
+ * left by 4 would mean that upper 44 bits are still zero
+ */
+ dst_reg->imm -= insn->imm;
+ } else if (dst_reg->imm && opcode == BPF_MUL) {
+ /* reg *= imm
+ * if multiplying by 14 subtract 4
+ * This is conservative calculation of upper zero bits.
+ * It's not trying to special case insn->imm == 1 or 0 cases
+ */
+ dst_reg->imm -= imm_log2 + 1;
+ } else if (opcode == BPF_AND) {
+ /* reg &= imm */
+ dst_reg->imm = 63 - imm_log2;
+ } else if (dst_reg->imm && opcode == BPF_ADD) {
+ /* reg += imm */
+ dst_reg->imm = min(dst_reg->imm, 63 - imm_log2);
+ dst_reg->imm--;
+ } else if (opcode == BPF_RSH) {
+ /* reg >>= imm
+ * which means that after right shift, upper bits will be zero
+ * note that verifier already checked that
+ * 0 <= imm < 64 for shift insn
+ */
+ dst_reg->imm += insn->imm;
+ if (unlikely(dst_reg->imm > 64))
+ /* some dumb code did:
+ * r2 = *(u32 *)mem;
+ * r2 >>= 32;
+ * and all bits are zero now */
+ dst_reg->imm = 64;
+ } else {
+ /* all other alu ops, means that we don't know what will
+ * happen to the value, mark it with unknown number of zero bits
+ */
+ dst_reg->imm = 0;
+ }
+
+ if (dst_reg->imm < 0) {
+ /* all 64 bits of the register can contain non-zero bits
+ * and such value cannot be added to ptr_to_packet, since it
+ * may overflow, mark it as unknown to avoid further eval
+ */
+ dst_reg->imm = 0;
+ }
+ return 0;
+}
+
+static int evaluate_reg_imm_alu(struct verifier_env *env, struct bpf_insn *insn)
+{
+ struct reg_state *regs = env->cur_state.regs;
+ struct reg_state *dst_reg = ®s[insn->dst_reg];
+ struct reg_state *src_reg = ®s[insn->src_reg];
+ u8 opcode = BPF_OP(insn->code);
+
+ /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn.
+ * Don't care about overflow or negative values, just add them
+ */
+ if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K)
+ dst_reg->imm += insn->imm;
+ else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X &&
+ src_reg->type == CONST_IMM)
+ dst_reg->imm += src_reg->imm;
+ else
+ mark_reg_unknown_value(regs, insn->dst_reg);
return 0;
}
dst_reg->type = PTR_TO_STACK;
dst_reg->imm = insn->imm;
return 0;
+ } else if (opcode == BPF_ADD &&
+ BPF_CLASS(insn->code) == BPF_ALU64 &&
+ dst_reg->type == PTR_TO_PACKET) {
+ /* ptr_to_packet += K|X */
+ return check_packet_ptr_add(env, insn);
+ } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
+ dst_reg->type == UNKNOWN_VALUE &&
+ env->allow_ptr_leaks) {
+ /* unknown += K|X */
+ return evaluate_reg_alu(env, insn);
+ } else if (BPF_CLASS(insn->code) == BPF_ALU64 &&
+ dst_reg->type == CONST_IMM &&
+ env->allow_ptr_leaks) {
+ /* reg_imm += K|X */
+ return evaluate_reg_imm_alu(env, insn);
} else if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer arithmetic prohibited\n",
insn->dst_reg);
return 0;
}
+static void find_good_pkt_pointers(struct verifier_env *env,
+ struct reg_state *dst_reg)
+{
+ struct verifier_state *state = &env->cur_state;
+ struct reg_state *regs = state->regs, *reg;
+ int i;
+ /* r2 = r3;
+ * r2 += 8
+ * if (r2 > pkt_end) goto somewhere
+ * r2 == dst_reg, pkt_end == src_reg,
+ * r2=pkt(id=n,off=8,r=0)
+ * r3=pkt(id=n,off=0,r=0)
+ * find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
+ * so that range of bytes [r3, r3 + 8) is safe to access
+ */
+ for (i = 0; i < MAX_BPF_REG; i++)
+ if (regs[i].type == PTR_TO_PACKET && regs[i].id == dst_reg->id)
+ regs[i].range = dst_reg->off;
+
+ for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
+ if (state->stack_slot_type[i] != STACK_SPILL)
+ continue;
+ reg = &state->spilled_regs[i / BPF_REG_SIZE];
+ if (reg->type == PTR_TO_PACKET && reg->id == dst_reg->id)
+ reg->range = dst_reg->off;
+ }
+}
+
static int check_cond_jmp_op(struct verifier_env *env,
struct bpf_insn *insn, int *insn_idx)
{
regs[insn->dst_reg].type = CONST_IMM;
regs[insn->dst_reg].imm = 0;
}
+ } else if (BPF_SRC(insn->code) == BPF_X && opcode == BPF_JGT &&
+ dst_reg->type == PTR_TO_PACKET &&
+ regs[insn->src_reg].type == PTR_TO_PACKET_END) {
+ find_good_pkt_pointers(env, dst_reg);
} else if (is_pointer_value(env, insn->dst_reg)) {
verbose("R%d pointer comparison prohibited\n", insn->dst_reg);
return -EACCES;
return ret;
}
+/* the following conditions reduce the number of explored insns
+ * from ~140k to ~80k for ultra large programs that use a lot of ptr_to_packet
+ */
+static bool compare_ptrs_to_packet(struct reg_state *old, struct reg_state *cur)
+{
+ if (old->id != cur->id)
+ return false;
+
+ /* old ptr_to_packet is more conservative, since it allows smaller
+ * range. Ex:
+ * old(off=0,r=10) is equal to cur(off=0,r=20), because
+ * old(off=0,r=10) means that with range=10 the verifier proceeded
+ * further and found no issues with the program. Now we're in the same
+ * spot with cur(off=0,r=20), so we're safe too, since anything further
+ * will only be looking at most 10 bytes after this pointer.
+ */
+ if (old->off == cur->off && old->range < cur->range)
+ return true;
+
+ /* old(off=20,r=10) is equal to cur(off=22,re=22 or 5 or 0)
+ * since both cannot be used for packet access and safe(old)
+ * pointer has smaller off that could be used for further
+ * 'if (ptr > data_end)' check
+ * Ex:
+ * old(off=20,r=10) and cur(off=22,r=22) and cur(off=22,r=0) mean
+ * that we cannot access the packet.
+ * The safe range is:
+ * [ptr, ptr + range - off)
+ * so whenever off >=range, it means no safe bytes from this pointer.
+ * When comparing old->off <= cur->off, it means that older code
+ * went with smaller offset and that offset was later
+ * used to figure out the safe range after 'if (ptr > data_end)' check
+ * Say, 'old' state was explored like:
+ * ... R3(off=0, r=0)
+ * R4 = R3 + 20
+ * ... now R4(off=20,r=0) <-- here
+ * if (R4 > data_end)
+ * ... R4(off=20,r=20), R3(off=0,r=20) and R3 can be used to access.
+ * ... the code further went all the way to bpf_exit.
+ * Now the 'cur' state at the mark 'here' has R4(off=30,r=0).
+ * old_R4(off=20,r=0) equal to cur_R4(off=30,r=0), since if the verifier
+ * goes further, such cur_R4 will give larger safe packet range after
+ * 'if (R4 > data_end)' and all further insn were already good with r=20,
+ * so they will be good with r=30 and we can prune the search.
+ */
+ if (old->off <= cur->off &&
+ old->off >= old->range && cur->off >= cur->range)
+ return true;
+
+ return false;
+}
+
/* compare two verifier states
*
* all states stored in state_list are known to be valid, since
(rold->type == UNKNOWN_VALUE && rcur->type != NOT_INIT))
continue;
+ if (rold->type == PTR_TO_PACKET && rcur->type == PTR_TO_PACKET &&
+ compare_ptrs_to_packet(rold, rcur))
+ continue;
+
return false;
}
projects / GitHub / MotorolaMobilityLLC / kernel-slsi.git / commitdiff