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path: root/arch/s390/net/bpf_jit_comp.c
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Diffstat (limited to 'arch/s390/net/bpf_jit_comp.c')
-rw-r--r--arch/s390/net/bpf_jit_comp.c113
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);
}