bpf: Prevent pointer mismatch in bpf_timer_init.

[linux-block.git] / include / linux / 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/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)

/* 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;
};

/* 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;

        /* The following fields should be last. See copy_func_state() */
        int acquired_refs;
        struct bpf_reference_state *refs;
        int allocated_stack;
        bool in_callback_fn;
        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))

/* 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 */
        int sanitize_stack_off; /* stack slot to be cleared */
        u32 seen; /* this insn was processed by the verifier at env->pass_cnt */
        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);
}

#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;
};

/* 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 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;
};

__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_ctx_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);

#endif /* _LINUX_BPF_VERIFIER_H */