diff options
Diffstat (limited to 'arch/s390/net/bpf_jit_comp.c')
| -rw-r--r-- | arch/s390/net/bpf_jit_comp.c | 113 |
1 files changed, 88 insertions, 25 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 82f165f..d5f10a4 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -9,6 +9,8 @@ #include <linux/netdevice.h> #include <linux/if_vlan.h> #include <linux/filter.h> +#include <linux/random.h> +#include <linux/init.h> #include <asm/cacheflush.h> #include <asm/processor.h> #include <asm/facility.h> @@ -221,6 +223,37 @@ static void bpf_jit_epilogue(struct bpf_jit *jit) EMIT2(0x07fe); } +/* Helper to find the offset of pkt_type in sk_buff + * Make sure its still a 3bit field starting at the MSBs within a byte. + */ +#define PKT_TYPE_MAX 0xe0 +static int pkt_type_offset; + +static int __init bpf_pkt_type_offset_init(void) +{ + struct sk_buff skb_probe = { + .pkt_type = ~0, + }; + char *ct = (char *)&skb_probe; + int off; + + pkt_type_offset = -1; + for (off = 0; off < sizeof(struct sk_buff); off++) { + if (!ct[off]) + continue; + if (ct[off] == PKT_TYPE_MAX) + pkt_type_offset = off; + else { + /* Found non matching bit pattern, fix needed. */ + WARN_ON_ONCE(1); + pkt_type_offset = -1; + return -1; + } + } + return 0; +} +device_initcall(bpf_pkt_type_offset_init); + /* * make sure we dont leak kernel information to user */ @@ -720,6 +753,16 @@ call_fn: /* lg %r1,<d(function)>(%r13) */ EMIT4_DISP(0x88500000, 12); } break; + case BPF_S_ANC_PKTTYPE: + if (pkt_type_offset < 0) + goto out; + /* lhi %r5,0 */ + EMIT4(0xa7580000); + /* ic %r5,<d(pkt_type_offset)>(%r2) */ + EMIT4_DISP(0x43502000, pkt_type_offset); + /* srl %r5,5 */ + EMIT4_DISP(0x88500000, 5); + break; case BPF_S_ANC_CPU: /* A = smp_processor_id() */ #ifdef CONFIG_SMP /* l %r5,<d(cpu_nr)> */ @@ -738,8 +781,41 @@ out: return -1; } +/* + * Note: for security reasons, bpf code will follow a randomly + * sized amount of illegal instructions. + */ +struct bpf_binary_header { + unsigned int pages; + u8 image[]; +}; + +static struct bpf_binary_header *bpf_alloc_binary(unsigned int bpfsize, + u8 **image_ptr) +{ + struct bpf_binary_header *header; + unsigned int sz, hole; + + /* Most BPF filters are really small, but if some of them fill a page, + * allow at least 128 extra bytes for illegal instructions. + */ + sz = round_up(bpfsize + sizeof(*header) + 128, PAGE_SIZE); + header = module_alloc(sz); + if (!header) + return NULL; + memset(header, 0, sz); + header->pages = sz / PAGE_SIZE; + hole = sz - bpfsize + sizeof(*header); + /* Insert random number of illegal instructions before BPF code + * and make sure the first instruction starts at an even address. + */ + *image_ptr = &header->image[(prandom_u32() % hole) & -2]; + return header; +} + void bpf_jit_compile(struct sk_filter *fp) { + struct bpf_binary_header *header = NULL; unsigned long size, prg_len, lit_len; struct bpf_jit jit, cjit; unsigned int *addrs; @@ -772,12 +848,11 @@ void bpf_jit_compile(struct sk_filter *fp) } else if (jit.prg == cjit.prg && jit.lit == cjit.lit) { prg_len = jit.prg - jit.start; lit_len = jit.lit - jit.mid; - size = max_t(unsigned long, prg_len + lit_len, - sizeof(struct work_struct)); + size = prg_len + lit_len; if (size >= BPF_SIZE_MAX) goto out; - jit.start = module_alloc(size); - if (!jit.start) + header = bpf_alloc_binary(size, &jit.start); + if (!header) goto out; jit.prg = jit.mid = jit.start + prg_len; jit.lit = jit.end = jit.start + prg_len + lit_len; @@ -788,37 +863,25 @@ void bpf_jit_compile(struct sk_filter *fp) cjit = jit; } if (bpf_jit_enable > 1) { - pr_err("flen=%d proglen=%lu pass=%d image=%p\n", - fp->len, jit.end - jit.start, pass, jit.start); - if (jit.start) { - printk(KERN_ERR "JIT code:\n"); + bpf_jit_dump(fp->len, jit.end - jit.start, pass, jit.start); + if (jit.start) print_fn_code(jit.start, jit.mid - jit.start); - print_hex_dump(KERN_ERR, "JIT literals:\n", - DUMP_PREFIX_ADDRESS, 16, 1, - jit.mid, jit.end - jit.mid, false); - } } - if (jit.start) + if (jit.start) { + set_memory_ro((unsigned long)header, header->pages); fp->bpf_func = (void *) jit.start; + } out: kfree(addrs); } -static void jit_free_defer(struct work_struct *arg) -{ - module_free(NULL, arg); -} - -/* run from softirq, we must use a work_struct to call - * module_free() from process context - */ void bpf_jit_free(struct sk_filter *fp) { - struct work_struct *work; + unsigned long addr = (unsigned long)fp->bpf_func & PAGE_MASK; + struct bpf_binary_header *header = (void *)addr; if (fp->bpf_func == sk_run_filter) return; - work = (struct work_struct *)fp->bpf_func; - INIT_WORK(work, jit_free_defer); - schedule_work(work); + set_memory_rw(addr, header->pages); + module_free(NULL, header); } |
