From: Daniel Borkmann Date: Sun, 4 Dec 2016 22:19:41 +0000 (+0100) Subject: bpf: add prog_digest and expose it via fdinfo/netlink X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7bd509e311f4;p=linux-beck.git bpf: add prog_digest and expose it via fdinfo/netlink When loading a BPF program via bpf(2), calculate the digest over the program's instruction stream and store it in struct bpf_prog's digest member. This is done at a point in time before any instructions are rewritten by the verifier. Any unstable map file descriptor number part of the imm field will be zeroed for the hash. fdinfo example output for progs: # cat /proc/1590/fdinfo/5 pos: 0 flags: 02000002 mnt_id: 11 prog_type: 1 prog_jited: 1 prog_digest: b27e8b06da22707513aa97363dfb11c7c3675d28 memlock: 4096 When programs are pinned and retrieved by an ELF loader, the loader can check the program's digest through fdinfo and compare it against one that was generated over the ELF file's program section to see if the program needs to be reloaded. Furthermore, this can also be exposed through other means such as netlink in case of a tc cls/act dump (or xdp in future), but also through tracepoints or other facilities to identify the program. Other than that, the digest can also serve as a base name for the work in progress kallsyms support of programs. The digest doesn't depend/select the crypto layer, since we need to keep dependencies to a minimum. iproute2 will get support for this facility. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 69d0a7f12a3b..8796ff03f472 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -216,6 +216,7 @@ u64 bpf_tail_call(u64 ctx, u64 r2, u64 index, u64 r4, u64 r5); u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp); +void bpf_prog_calc_digest(struct bpf_prog *fp); const struct bpf_func_proto *bpf_get_trace_printk_proto(void); diff --git a/include/linux/filter.h b/include/linux/filter.h index 97338134398f..f078d2b1cff6 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -14,6 +14,7 @@ #include #include #include +#include #include @@ -56,6 +57,9 @@ struct bpf_prog_aux; /* BPF program can access up to 512 bytes of stack space. */ #define MAX_BPF_STACK 512 +/* Maximum BPF program size in bytes. */ +#define MAX_BPF_SIZE (BPF_MAXINSNS * sizeof(struct bpf_insn)) + /* Helper macros for filter block array initializers. */ /* ALU ops on registers, bpf_add|sub|...: dst_reg += src_reg */ @@ -404,8 +408,9 @@ struct bpf_prog { cb_access:1, /* Is control block accessed? */ dst_needed:1; /* Do we need dst entry? */ kmemcheck_bitfield_end(meta); - u32 len; /* Number of filter blocks */ enum bpf_prog_type type; /* Type of BPF program */ + u32 len; /* Number of filter blocks */ + u32 digest[SHA_DIGEST_WORDS]; /* Program digest */ struct bpf_prog_aux *aux; /* Auxiliary fields */ struct sock_fprog_kern *orig_prog; /* Original BPF program */ unsigned int (*bpf_func)(const void *ctx, diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h index 86786d45ee66..1adc0b654996 100644 --- a/include/uapi/linux/pkt_cls.h +++ b/include/uapi/linux/pkt_cls.h @@ -397,6 +397,7 @@ enum { TCA_BPF_NAME, TCA_BPF_FLAGS, TCA_BPF_FLAGS_GEN, + TCA_BPF_DIGEST, __TCA_BPF_MAX, }; diff --git a/include/uapi/linux/tc_act/tc_bpf.h b/include/uapi/linux/tc_act/tc_bpf.h index 063d9d465119..a6b88a6f7f71 100644 --- a/include/uapi/linux/tc_act/tc_bpf.h +++ b/include/uapi/linux/tc_act/tc_bpf.h @@ -27,6 +27,7 @@ enum { TCA_ACT_BPF_FD, TCA_ACT_BPF_NAME, TCA_ACT_BPF_PAD, + TCA_ACT_BPF_DIGEST, __TCA_ACT_BPF_MAX, }; #define TCA_ACT_BPF_MAX (__TCA_ACT_BPF_MAX - 1) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 82a04143368e..bdcc9f4ba767 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -136,6 +136,71 @@ void __bpf_prog_free(struct bpf_prog *fp) vfree(fp); } +#define SHA_BPF_RAW_SIZE \ + round_up(MAX_BPF_SIZE + sizeof(__be64) + 1, SHA_MESSAGE_BYTES) + +/* Called under verifier mutex. */ +void bpf_prog_calc_digest(struct bpf_prog *fp) +{ + const u32 bits_offset = SHA_MESSAGE_BYTES - sizeof(__be64); + static u32 ws[SHA_WORKSPACE_WORDS]; + static u8 raw[SHA_BPF_RAW_SIZE]; + struct bpf_insn *dst = (void *)raw; + u32 i, bsize, psize, blocks; + bool was_ld_map; + u8 *todo = raw; + __be32 *result; + __be64 *bits; + + sha_init(fp->digest); + memset(ws, 0, sizeof(ws)); + + /* We need to take out the map fd for the digest calculation + * since they are unstable from user space side. + */ + for (i = 0, was_ld_map = false; i < fp->len; i++) { + dst[i] = fp->insnsi[i]; + if (!was_ld_map && + dst[i].code == (BPF_LD | BPF_IMM | BPF_DW) && + dst[i].src_reg == BPF_PSEUDO_MAP_FD) { + was_ld_map = true; + dst[i].imm = 0; + } else if (was_ld_map && + dst[i].code == 0 && + dst[i].dst_reg == 0 && + dst[i].src_reg == 0 && + dst[i].off == 0) { + was_ld_map = false; + dst[i].imm = 0; + } else { + was_ld_map = false; + } + } + + psize = fp->len * sizeof(struct bpf_insn); + memset(&raw[psize], 0, sizeof(raw) - psize); + raw[psize++] = 0x80; + + bsize = round_up(psize, SHA_MESSAGE_BYTES); + blocks = bsize / SHA_MESSAGE_BYTES; + if (bsize - psize >= sizeof(__be64)) { + bits = (__be64 *)(todo + bsize - sizeof(__be64)); + } else { + bits = (__be64 *)(todo + bsize + bits_offset); + blocks++; + } + *bits = cpu_to_be64((psize - 1) << 3); + + while (blocks--) { + sha_transform(fp->digest, todo, ws); + todo += SHA_MESSAGE_BYTES; + } + + result = (__force __be32 *)fp->digest; + for (i = 0; i < SHA_DIGEST_WORDS; i++) + result[i] = cpu_to_be32(fp->digest[i]); +} + static bool bpf_is_jmp_and_has_target(const struct bpf_insn *insn) { return BPF_CLASS(insn->code) == BPF_JMP && diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 85af86c496cd..c0d2b423ce93 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -662,8 +662,30 @@ static int bpf_prog_release(struct inode *inode, struct file *filp) return 0; } +#ifdef CONFIG_PROC_FS +static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp) +{ + const struct bpf_prog *prog = filp->private_data; + char prog_digest[sizeof(prog->digest) * 2 + 1] = { }; + + bin2hex(prog_digest, prog->digest, sizeof(prog->digest)); + seq_printf(m, + "prog_type:\t%u\n" + "prog_jited:\t%u\n" + "prog_digest:\t%s\n" + "memlock:\t%llu\n", + prog->type, + prog->jited, + prog_digest, + prog->pages * 1ULL << PAGE_SHIFT); +} +#endif + static const struct file_operations bpf_prog_fops = { - .release = bpf_prog_release, +#ifdef CONFIG_PROC_FS + .show_fdinfo = bpf_prog_show_fdinfo, +#endif + .release = bpf_prog_release, }; int bpf_prog_new_fd(struct bpf_prog *prog) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 38d05da84a49..cb37339ca0da 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3176,6 +3176,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) log_level = 0; } + bpf_prog_calc_digest(env->prog); + ret = replace_map_fd_with_map_ptr(env); if (ret < 0) goto skip_full_check; diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c index 84c1d2da4f8b..1c60317f0121 100644 --- a/net/sched/act_bpf.c +++ b/net/sched/act_bpf.c @@ -117,10 +117,19 @@ static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog, static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog, struct sk_buff *skb) { + struct nlattr *nla; + if (prog->bpf_name && nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name)) return -EMSGSIZE; + nla = nla_reserve(skb, TCA_ACT_BPF_DIGEST, + sizeof(prog->filter->digest)); + if (nla == NULL) + return -EMSGSIZE; + + memcpy(nla_data(nla), prog->filter->digest, nla_len(nla)); + return 0; } diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c index f70e03d2d2c8..adc776048d1a 100644 --- a/net/sched/cls_bpf.c +++ b/net/sched/cls_bpf.c @@ -549,10 +549,18 @@ static int cls_bpf_dump_bpf_info(const struct cls_bpf_prog *prog, static int cls_bpf_dump_ebpf_info(const struct cls_bpf_prog *prog, struct sk_buff *skb) { + struct nlattr *nla; + if (prog->bpf_name && nla_put_string(skb, TCA_BPF_NAME, prog->bpf_name)) return -EMSGSIZE; + nla = nla_reserve(skb, TCA_BPF_DIGEST, sizeof(prog->filter->digest)); + if (nla == NULL) + return -EMSGSIZE; + + memcpy(nla_data(nla), prog->filter->digest, nla_len(nla)); + return 0; }