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/* 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/btf.h> /* for struct btf and btf_id() */
#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)
/* size of type_str_buf in bpf_verifier. */
#define TYPE_STR_BUF_LEN 64
/* 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;
/* Fixed part of pointer offset, pointer types only */
s32 off;
union {
/* valid when type == PTR_TO_PACKET */
int range;
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
* PTR_TO_MAP_VALUE_OR_NULL
*/
struct {
struct bpf_map *map_ptr;
/* To distinguish map lookups from outer map
* the map_uid is non-zero for registers
* pointing to inner maps.
*/
u32 map_uid;
};
/* for PTR_TO_BTF_ID */
struct {
struct btf *btf;
u32 btf_id;
};
u32 mem_size; /* for PTR_TO_MEM | PTR_TO_MEM_OR_NULL */
/* Max size from any of the above. */
struct {
unsigned long raw1;
unsigned long raw2;
} raw;
u32 subprogno; /* for PTR_TO_FUNC */
};
/* 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_MEM_OR_NULL this is used to identify memory allocation
* for the purpose of tracking that it's freed.
* 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 */
s32 s32_min_value; /* minimum possible (s32)value */
s32 s32_max_value; /* maximum possible (s32)value */
u32 u32_min_value; /* minimum possible (u32)value */
u32 u32_max_value; /* maximum possible (u32)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;
/* There can be a case like:
* main (frame 0)
* cb (frame 1)
* func (frame 3)
* cb (frame 4)
* Hence for frame 4, if callback_ref just stored boolean, it would be
* impossible to distinguish nested callback refs. Hence store the
* frameno and compare that to callback_ref in check_reference_leak when
* exiting a callback function.
*/
int callback_ref;
};
/* 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_info
* zero == main subprog
*/
u32 subprogno;
/* Every bpf_timer_start will increment async_entry_cnt.
* It's used to distinguish:
* void foo(void) { for(;;); }
* void foo(void) { bpf_timer_set_callback(,foo); }
*/
u32 async_entry_cnt;
bool in_callback_fn;
bool in_async_callback_fn;
/* 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;
};
struct bpf_id_pair {
u32 old;
u32 cur;
};
/* Maximum number of register states that can exist at once */
#define BPF_ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
#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))
/* Invoke __expr over regsiters in __vst, setting __state and __reg */
#define bpf_for_each_reg_in_vstate(__vst, __state, __reg, __expr) \
({ \
struct bpf_verifier_state *___vstate = __vst; \
int ___i, ___j; \
for (___i = 0; ___i <= ___vstate->curframe; ___i++) { \
struct bpf_reg_state *___regs; \
__state = ___vstate->frame[___i]; \
___regs = __state->regs; \
for (___j = 0; ___j < MAX_BPF_REG; ___j++) { \
__reg = &___regs[___j]; \
(void)(__expr); \
} \
bpf_for_each_spilled_reg(___j, __state, __reg) { \
if (!__reg) \
continue; \
(void)(__expr); \
} \
} \
})
/* 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 << 0)
#define BPF_ALU_SANITIZE_DST (1U << 1)
#define BPF_ALU_NEG_VALUE (1U << 2)
#define BPF_ALU_NON_POINTER (1U << 3)
#define BPF_ALU_IMMEDIATE (1U << 4)
#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_ptr_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 */
};
struct {
enum bpf_reg_type reg_type; /* type of pseudo_btf_id */
union {
struct {
struct btf *btf;
u32 btf_id; /* btf_id for struct typed var */
};
u32 mem_size; /* mem_size for non-struct typed var */
};
} btf_var;
};
u64 map_key_state; /* constant (32 bit) key tracking for maps */
int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
u32 seen; /* this insn was processed by the verifier at env->pass_cnt */
bool sanitize_stack_spill; /* subject to Spectre v4 sanitation */
bool zext_dst; /* this insn zero extends dst reg */
u8 alu_state; /* used in combination with alu_limit */
/* below fields are initialized once */
unsigned int orig_idx; /* original instruction index */
bool prune_point;
};
#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
#define MAX_USED_BTFS 64 /* max number of BTFs accessed by one BPF 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)
#define BPF_LOG_KERNEL (BPF_LOG_MASK + 1) /* kernel internal flag */
static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
{
return log &&
((log->level && log->ubuf && !bpf_verifier_log_full(log)) ||
log->level == BPF_LOG_KERNEL);
}
static inline bool
bpf_verifier_log_attr_valid(const struct bpf_verifier_log *log)
{
return log->len_total >= 128 && log->len_total <= UINT_MAX >> 2 &&
log->level && log->ubuf && !(log->level & ~BPF_LOG_MASK);
}
#define BPF_MAX_SUBPROGS 256
struct bpf_subprog_info {
/* 'start' has to be the first field otherwise find_subprog() won't work */
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 */
bool has_tail_call;
bool tail_call_reachable;
bool has_ld_abs;
bool is_async_cb;
};
/* 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 */
struct btf_mod_pair used_btfs[MAX_USED_BTFS]; /* array of BTF's used by BPF program */
u32 used_map_cnt; /* number of used maps */
u32 used_btf_cnt; /* number of used BTF objects */
u32 id_gen; /* used to generate unique reg IDs */
bool explore_alu_limits;
bool allow_ptr_leaks;
bool allow_uninit_stack;
bool allow_ptr_to_map_access;
bool bpf_capable;
bool bypass_spec_v1;
bool bypass_spec_v4;
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 bpf_id_pair idmap_scratch[BPF_ID_MAP_SIZE];
struct {
int *insn_state;
int *insn_stack;
int cur_stack;
} cfg;
u32 pass_cnt; /* number of times do_check() was called */
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;
bpfptr_t fd_array;
/* buffer used in reg_type_str() to generate reg_type string */
char type_str_buf[TYPE_STR_BUF_LEN];
};
__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, ...);
__printf(2, 3) void bpf_log(struct bpf_verifier_log *log,
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);
int check_ptr_off_reg(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg, int regno);
int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
u32 regno, u32 mem_size);
/* this lives here instead of in bpf.h because it needs to dereference tgt_prog */
static inline u64 bpf_trampoline_compute_key(const struct bpf_prog *tgt_prog,
struct btf *btf, u32 btf_id)
{
if (tgt_prog)
return ((u64)tgt_prog->aux->id << 32) | btf_id;
else
return ((u64)btf_obj_id(btf) << 32) | 0x80000000 | btf_id;
}
/* unpack the IDs from the key as constructed above */
static inline void bpf_trampoline_unpack_key(u64 key, u32 *obj_id, u32 *btf_id)
{
if (obj_id)
*obj_id = key >> 32;
if (btf_id)
*btf_id = key & 0x7FFFFFFF;
}
int bpf_check_attach_target(struct bpf_verifier_log *log,
const struct bpf_prog *prog,
const struct bpf_prog *tgt_prog,
u32 btf_id,
struct bpf_attach_target_info *tgt_info);
#define BPF_BASE_TYPE_MASK GENMASK(BPF_BASE_TYPE_BITS - 1, 0)
/* extract base type from bpf_{arg, return, reg}_type. */
static inline u32 base_type(u32 type)
{
return type & BPF_BASE_TYPE_MASK;
}
/* extract flags from an extended type. See bpf_type_flag in bpf.h. */
static inline u32 type_flag(u32 type)
{
return type & ~BPF_BASE_TYPE_MASK;
}
#endif /* _LINUX_BPF_VERIFIER_H */
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