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authorDaniel Borkmann <dborkman@redhat.com>2014-09-08 08:04:47 +0200
committerDavid S. Miller <davem@davemloft.net>2014-09-09 16:58:56 -0700
commit738cbe72adc5c8f2016c4c68aa5162631d4f27e1 (patch)
tree4c207c0a763ea8998dddda89a7a1d9eb98866b60 /arch/s390/net
parentca777eff51f7fbaebd954e645d8ecb781a906b4a (diff)
downloadlinux-738cbe72adc5c8f2016c4c68aa5162631d4f27e1.tar.gz
net: bpf: consolidate JIT binary allocator
Introduced in commit 314beb9bcabf ("x86: bpf_jit_comp: secure bpf jit against spraying attacks") and later on replicated in aa2d2c73c21f ("s390/bpf,jit: address randomize and write protect jit code") for s390 architecture, write protection for BPF JIT images got added and a random start address of the JIT code, so that it's not on a page boundary anymore. Since both use a very similar allocator for the BPF binary header, we can consolidate this code into the BPF core as it's mostly JIT independant anyway. This will also allow for future archs that support DEBUG_SET_MODULE_RONX to just reuse instead of reimplementing it. JIT tested on x86_64 and s390x with BPF test suite. Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Acked-by: Alexei Starovoitov <ast@plumgrid.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/s390/net')
-rw-r--r--arch/s390/net/bpf_jit_comp.c45
1 files changed, 9 insertions, 36 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index f2833c5b218a..b734f975c22e 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -5,11 +5,9 @@
*
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
-#include <linux/moduleloader.h>
#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/facility.h>
@@ -148,6 +146,12 @@ struct bpf_jit {
ret; \
})
+static void bpf_jit_fill_hole(void *area, unsigned int size)
+{
+ /* Fill whole space with illegal instructions */
+ memset(area, 0, size);
+}
+
static void bpf_jit_prologue(struct bpf_jit *jit)
{
/* Save registers and create stack frame if necessary */
@@ -780,38 +784,6 @@ 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 = min(sz - (bpfsize + sizeof(*header)), PAGE_SIZE - 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 bpf_prog *fp)
{
struct bpf_binary_header *header = NULL;
@@ -850,7 +822,8 @@ void bpf_jit_compile(struct bpf_prog *fp)
size = prg_len + lit_len;
if (size >= BPF_SIZE_MAX)
goto out;
- header = bpf_alloc_binary(size, &jit.start);
+ header = bpf_jit_binary_alloc(size, &jit.start,
+ 2, bpf_jit_fill_hole);
if (!header)
goto out;
jit.prg = jit.mid = jit.start + prg_len;
@@ -884,7 +857,7 @@ void bpf_jit_free(struct bpf_prog *fp)
goto free_filter;
set_memory_rw(addr, header->pages);
- module_free(NULL, header);
+ bpf_jit_binary_free(header);
free_filter:
bpf_prog_unlock_free(fp);