https://github.com/torvalds/linux
Tip revision: da0c9ea146cbe92b832f1b0f694840ea8eb33cce authored by Linus Torvalds on 06 October 2019, 21:27:30 UTC
Linux 5.4-rc2
Linux 5.4-rc2
Tip revision: da0c9ea
bpf_verifier.h
/* SPDX-License-Identifier: GPL-2.0-only */
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
*/
#ifndef _LINUX_BPF_VERIFIER_H
#define _LINUX_BPF_VERIFIER_H 1
#include <linux/bpf.h> /* for enum bpf_reg_type */
#include <linux/filter.h> /* for MAX_BPF_STACK */
#include <linux/tnum.h>
/* Maximum variable offset umax_value permitted when resolving memory accesses.
* In practice this is far bigger than any realistic pointer offset; this limit
* ensures that umax_value + (int)off + (int)size cannot overflow a u64.
*/
#define BPF_MAX_VAR_OFF (1 << 29)
/* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures
* that converting umax_value to int cannot overflow.
*/
#define BPF_MAX_VAR_SIZ (1 << 29)
/* Liveness marks, used for registers and spilled-regs (in stack slots).
* Read marks propagate upwards until they find a write mark; they record that
* "one of this state's descendants read this reg" (and therefore the reg is
* relevant for states_equal() checks).
* Write marks collect downwards and do not propagate; they record that "the
* straight-line code that reached this state (from its parent) wrote this reg"
* (and therefore that reads propagated from this state or its descendants
* should not propagate to its parent).
* A state with a write mark can receive read marks; it just won't propagate
* them to its parent, since the write mark is a property, not of the state,
* but of the link between it and its parent. See mark_reg_read() and
* mark_stack_slot_read() in kernel/bpf/verifier.c.
*/
enum bpf_reg_liveness {
REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
REG_LIVE_READ32 = 0x1, /* reg was read, so we're sensitive to initial value */
REG_LIVE_READ64 = 0x2, /* likewise, but full 64-bit content matters */
REG_LIVE_READ = REG_LIVE_READ32 | REG_LIVE_READ64,
REG_LIVE_WRITTEN = 0x4, /* reg was written first, screening off later reads */
REG_LIVE_DONE = 0x8, /* liveness won't be updating this register anymore */
};
struct bpf_reg_state {
/* Ordering of fields matters. See states_equal() */
enum bpf_reg_type type;
union {
/* valid when type == PTR_TO_PACKET */
u16 range;
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
* PTR_TO_MAP_VALUE_OR_NULL
*/
struct bpf_map *map_ptr;
/* Max size from any of the above. */
unsigned long raw;
};
/* Fixed part of pointer offset, pointer types only */
s32 off;
/* For PTR_TO_PACKET, used to find other pointers with the same variable
* offset, so they can share range knowledge.
* For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
* came from, when one is tested for != NULL.
* For PTR_TO_SOCKET this is used to share which pointers retain the
* same reference to the socket, to determine proper reference freeing.
*/
u32 id;
/* PTR_TO_SOCKET and PTR_TO_TCP_SOCK could be a ptr returned
* from a pointer-cast helper, bpf_sk_fullsock() and
* bpf_tcp_sock().
*
* Consider the following where "sk" is a reference counted
* pointer returned from "sk = bpf_sk_lookup_tcp();":
*
* 1: sk = bpf_sk_lookup_tcp();
* 2: if (!sk) { return 0; }
* 3: fullsock = bpf_sk_fullsock(sk);
* 4: if (!fullsock) { bpf_sk_release(sk); return 0; }
* 5: tp = bpf_tcp_sock(fullsock);
* 6: if (!tp) { bpf_sk_release(sk); return 0; }
* 7: bpf_sk_release(sk);
* 8: snd_cwnd = tp->snd_cwnd; // verifier will complain
*
* After bpf_sk_release(sk) at line 7, both "fullsock" ptr and
* "tp" ptr should be invalidated also. In order to do that,
* the reg holding "fullsock" and "sk" need to remember
* the original refcounted ptr id (i.e. sk_reg->id) in ref_obj_id
* such that the verifier can reset all regs which have
* ref_obj_id matching the sk_reg->id.
*
* sk_reg->ref_obj_id is set to sk_reg->id at line 1.
* sk_reg->id will stay as NULL-marking purpose only.
* After NULL-marking is done, sk_reg->id can be reset to 0.
*
* After "fullsock = bpf_sk_fullsock(sk);" at line 3,
* fullsock_reg->ref_obj_id is set to sk_reg->ref_obj_id.
*
* After "tp = bpf_tcp_sock(fullsock);" at line 5,
* tp_reg->ref_obj_id is set to fullsock_reg->ref_obj_id
* which is the same as sk_reg->ref_obj_id.
*
* From the verifier perspective, if sk, fullsock and tp
* are not NULL, they are the same ptr with different
* reg->type. In particular, bpf_sk_release(tp) is also
* allowed and has the same effect as bpf_sk_release(sk).
*/
u32 ref_obj_id;
/* For scalar types (SCALAR_VALUE), this represents our knowledge of
* the actual value.
* For pointer types, this represents the variable part of the offset
* from the pointed-to object, and is shared with all bpf_reg_states
* with the same id as us.
*/
struct tnum var_off;
/* Used to determine if any memory access using this register will
* result in a bad access.
* These refer to the same value as var_off, not necessarily the actual
* contents of the register.
*/
s64 smin_value; /* minimum possible (s64)value */
s64 smax_value; /* maximum possible (s64)value */
u64 umin_value; /* minimum possible (u64)value */
u64 umax_value; /* maximum possible (u64)value */
/* parentage chain for liveness checking */
struct bpf_reg_state *parent;
/* Inside the callee two registers can be both PTR_TO_STACK like
* R1=fp-8 and R2=fp-8, but one of them points to this function stack
* while another to the caller's stack. To differentiate them 'frameno'
* is used which is an index in bpf_verifier_state->frame[] array
* pointing to bpf_func_state.
*/
u32 frameno;
/* Tracks subreg definition. The stored value is the insn_idx of the
* writing insn. This is safe because subreg_def is used before any insn
* patching which only happens after main verification finished.
*/
s32 subreg_def;
enum bpf_reg_liveness live;
/* if (!precise && SCALAR_VALUE) min/max/tnum don't affect safety */
bool precise;
};
enum bpf_stack_slot_type {
STACK_INVALID, /* nothing was stored in this stack slot */
STACK_SPILL, /* register spilled into stack */
STACK_MISC, /* BPF program wrote some data into this slot */
STACK_ZERO, /* BPF program wrote constant zero */
};
#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
struct bpf_stack_state {
struct bpf_reg_state spilled_ptr;
u8 slot_type[BPF_REG_SIZE];
};
struct bpf_reference_state {
/* Track each reference created with a unique id, even if the same
* instruction creates the reference multiple times (eg, via CALL).
*/
int id;
/* Instruction where the allocation of this reference occurred. This
* is used purely to inform the user of a reference leak.
*/
int insn_idx;
};
/* state of the program:
* type of all registers and stack info
*/
struct bpf_func_state {
struct bpf_reg_state regs[MAX_BPF_REG];
/* index of call instruction that called into this func */
int callsite;
/* stack frame number of this function state from pov of
* enclosing bpf_verifier_state.
* 0 = main function, 1 = first callee.
*/
u32 frameno;
/* subprog number == index within subprog_stack_depth
* zero == main subprog
*/
u32 subprogno;
/* The following fields should be last. See copy_func_state() */
int acquired_refs;
struct bpf_reference_state *refs;
int allocated_stack;
struct bpf_stack_state *stack;
};
struct bpf_idx_pair {
u32 prev_idx;
u32 idx;
};
#define MAX_CALL_FRAMES 8
struct bpf_verifier_state {
/* call stack tracking */
struct bpf_func_state *frame[MAX_CALL_FRAMES];
struct bpf_verifier_state *parent;
/*
* 'branches' field is the number of branches left to explore:
* 0 - all possible paths from this state reached bpf_exit or
* were safely pruned
* 1 - at least one path is being explored.
* This state hasn't reached bpf_exit
* 2 - at least two paths are being explored.
* This state is an immediate parent of two children.
* One is fallthrough branch with branches==1 and another
* state is pushed into stack (to be explored later) also with
* branches==1. The parent of this state has branches==1.
* The verifier state tree connected via 'parent' pointer looks like:
* 1
* 1
* 2 -> 1 (first 'if' pushed into stack)
* 1
* 2 -> 1 (second 'if' pushed into stack)
* 1
* 1
* 1 bpf_exit.
*
* Once do_check() reaches bpf_exit, it calls update_branch_counts()
* and the verifier state tree will look:
* 1
* 1
* 2 -> 1 (first 'if' pushed into stack)
* 1
* 1 -> 1 (second 'if' pushed into stack)
* 0
* 0
* 0 bpf_exit.
* After pop_stack() the do_check() will resume at second 'if'.
*
* If is_state_visited() sees a state with branches > 0 it means
* there is a loop. If such state is exactly equal to the current state
* it's an infinite loop. Note states_equal() checks for states
* equvalency, so two states being 'states_equal' does not mean
* infinite loop. The exact comparison is provided by
* states_maybe_looping() function. It's a stronger pre-check and
* much faster than states_equal().
*
* This algorithm may not find all possible infinite loops or
* loop iteration count may be too high.
* In such cases BPF_COMPLEXITY_LIMIT_INSNS limit kicks in.
*/
u32 branches;
u32 insn_idx;
u32 curframe;
u32 active_spin_lock;
bool speculative;
/* first and last insn idx of this verifier state */
u32 first_insn_idx;
u32 last_insn_idx;
/* jmp history recorded from first to last.
* backtracking is using it to go from last to first.
* For most states jmp_history_cnt is [0-3].
* For loops can go up to ~40.
*/
struct bpf_idx_pair *jmp_history;
u32 jmp_history_cnt;
};
#define bpf_get_spilled_reg(slot, frame) \
(((slot < frame->allocated_stack / BPF_REG_SIZE) && \
(frame->stack[slot].slot_type[0] == STACK_SPILL)) \
? &frame->stack[slot].spilled_ptr : NULL)
/* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
#define bpf_for_each_spilled_reg(iter, frame, reg) \
for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \
iter < frame->allocated_stack / BPF_REG_SIZE; \
iter++, reg = bpf_get_spilled_reg(iter, frame))
/* linked list of verifier states used to prune search */
struct bpf_verifier_state_list {
struct bpf_verifier_state state;
struct bpf_verifier_state_list *next;
int miss_cnt, hit_cnt;
};
/* Possible states for alu_state member. */
#define BPF_ALU_SANITIZE_SRC 1U
#define BPF_ALU_SANITIZE_DST 2U
#define BPF_ALU_NEG_VALUE (1U << 2)
#define BPF_ALU_NON_POINTER (1U << 3)
#define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
BPF_ALU_SANITIZE_DST)
struct bpf_insn_aux_data {
union {
enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
unsigned long map_state; /* pointer/poison value for maps */
s32 call_imm; /* saved imm field of call insn */
u32 alu_limit; /* limit for add/sub register with pointer */
struct {
u32 map_index; /* index into used_maps[] */
u32 map_off; /* offset from value base address */
};
};
int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
int sanitize_stack_off; /* stack slot to be cleared */
bool seen; /* this insn was processed by the verifier */
bool zext_dst; /* this insn zero extends dst reg */
u8 alu_state; /* used in combination with alu_limit */
bool prune_point;
unsigned int orig_idx; /* original instruction index */
};
#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
#define BPF_VERIFIER_TMP_LOG_SIZE 1024
struct bpf_verifier_log {
u32 level;
char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
char __user *ubuf;
u32 len_used;
u32 len_total;
};
static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
{
return log->len_used >= log->len_total - 1;
}
#define BPF_LOG_LEVEL1 1
#define BPF_LOG_LEVEL2 2
#define BPF_LOG_STATS 4
#define BPF_LOG_LEVEL (BPF_LOG_LEVEL1 | BPF_LOG_LEVEL2)
#define BPF_LOG_MASK (BPF_LOG_LEVEL | BPF_LOG_STATS)
static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
{
return log->level && log->ubuf && !bpf_verifier_log_full(log);
}
#define BPF_MAX_SUBPROGS 256
struct bpf_subprog_info {
u32 start; /* insn idx of function entry point */
u32 linfo_idx; /* The idx to the main_prog->aux->linfo */
u16 stack_depth; /* max. stack depth used by this function */
};
/* single container for all structs
* one verifier_env per bpf_check() call
*/
struct bpf_verifier_env {
u32 insn_idx;
u32 prev_insn_idx;
struct bpf_prog *prog; /* eBPF program being verified */
const struct bpf_verifier_ops *ops;
struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
int stack_size; /* number of states to be processed */
bool strict_alignment; /* perform strict pointer alignment checks */
bool test_state_freq; /* test verifier with different pruning frequency */
struct bpf_verifier_state *cur_state; /* current verifier state */
struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
struct bpf_verifier_state_list *free_list;
struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
u32 used_map_cnt; /* number of used maps */
u32 id_gen; /* used to generate unique reg IDs */
bool allow_ptr_leaks;
bool seen_direct_write;
struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
const struct bpf_line_info *prev_linfo;
struct bpf_verifier_log log;
struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
struct {
int *insn_state;
int *insn_stack;
int cur_stack;
} cfg;
u32 subprog_cnt;
/* number of instructions analyzed by the verifier */
u32 prev_insn_processed, insn_processed;
/* number of jmps, calls, exits analyzed so far */
u32 prev_jmps_processed, jmps_processed;
/* total verification time */
u64 verification_time;
/* maximum number of verifier states kept in 'branching' instructions */
u32 max_states_per_insn;
/* total number of allocated verifier states */
u32 total_states;
/* some states are freed during program analysis.
* this is peak number of states. this number dominates kernel
* memory consumption during verification
*/
u32 peak_states;
/* longest register parentage chain walked for liveness marking */
u32 longest_mark_read_walk;
};
__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
const char *fmt, va_list args);
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
const char *fmt, ...);
static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
{
struct bpf_verifier_state *cur = env->cur_state;
return cur->frame[cur->curframe];
}
static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
{
return cur_func(env)->regs;
}
int bpf_prog_offload_verifier_prep(struct bpf_prog *prog);
int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx);
int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
void
bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
struct bpf_insn *insn);
void
bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
#endif /* _LINUX_BPF_VERIFIER_H */