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 82f165f8078c..d5f10a43a58f 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);
 }