Skip to content

Commit

Permalink
bpf: export helper function flags and reject invalid ones
Browse files Browse the repository at this point in the history 
Export flags used by eBPF helper functions through UAPI, so they can be
used by programs (instead of them redefining all flags each time or just
using the hard-coded values). It also gives a better overview what flags
are used where and we can further get rid of the extra macros defined in
filter.c. Moreover, reject invalid flags.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
  • Loading branch information
@borkmann @davem330
borkmann authored and davem330 committed Jan 11, 2016
1 parent c8086f6 commit 781c53b
Show file tree
Hide file tree
Showing 2 changed files with 39 additions and 14 deletions.
16 changes: 16 additions & 0 deletions include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -273,6 +273,22 @@ enum bpf_func_id {
__BPF_FUNC_MAX_ID,
};

/* All flags used by eBPF helper functions, placed here. */

/* BPF_FUNC_skb_store_bytes flags. */
#define BPF_F_RECOMPUTE_CSUM (1ULL << 0)

/* BPF_FUNC_l3_csum_replace and BPF_FUNC_l4_csum_replace flags.
* First 4 bits are for passing the header field size.
*/
#define BPF_F_HDR_FIELD_MASK 0xfULL

/* BPF_FUNC_l4_csum_replace flags. */
#define BPF_F_PSEUDO_HDR (1ULL << 4)

/* BPF_FUNC_clone_redirect and BPF_FUNC_redirect flags. */
#define BPF_F_INGRESS (1ULL << 0)

/* user accessible mirror of in-kernel sk_buff.
* new fields can only be added to the end of this structure
*/
Expand Down
37 changes: 23 additions & 14 deletions net/core/filter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1328,8 +1328,7 @@ int sk_reuseport_attach_bpf(u32 ufd, struct sock *sk)
return 0;
}

#define BPF_RECOMPUTE_CSUM(flags) ((flags) & 1)
#define BPF_LDST_LEN 16U
#define BPF_LDST_LEN 16U

static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
{
Expand All @@ -1340,6 +1339,9 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
char buf[BPF_LDST_LEN];
void *ptr;

if (unlikely(flags & ~(BPF_F_RECOMPUTE_CSUM)))
return -EINVAL;

/* bpf verifier guarantees that:
* 'from' pointer points to bpf program stack
* 'len' bytes of it were initialized
Expand All @@ -1359,7 +1361,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
if (unlikely(!ptr))
return -EFAULT;

if (BPF_RECOMPUTE_CSUM(flags))
if (flags & BPF_F_RECOMPUTE_CSUM)
skb_postpull_rcsum(skb, ptr, len);

memcpy(ptr, from, len);
Expand All @@ -1368,7 +1370,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
/* skb_store_bits cannot return -EFAULT here */
skb_store_bits(skb, offset, ptr, len);

if (BPF_RECOMPUTE_CSUM(flags))
if (flags & BPF_F_RECOMPUTE_CSUM)
skb_postpush_rcsum(skb, ptr, len);

return 0;
Expand Down Expand Up @@ -1415,15 +1417,14 @@ const struct bpf_func_proto bpf_skb_load_bytes_proto = {
.arg4_type = ARG_CONST_STACK_SIZE,
};

#define BPF_HEADER_FIELD_SIZE(flags) ((flags) & 0x0f)
#define BPF_IS_PSEUDO_HEADER(flags) ((flags) & 0x10)

static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
{
struct sk_buff *skb = (struct sk_buff *) (long) r1;
int offset = (int) r2;
__sum16 sum, *ptr;

if (unlikely(flags & ~(BPF_F_HDR_FIELD_MASK)))
return -EINVAL;
if (unlikely((u32) offset > 0xffff))
return -EFAULT;

Expand All @@ -1435,7 +1436,7 @@ static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
if (unlikely(!ptr))
return -EFAULT;

switch (BPF_HEADER_FIELD_SIZE(flags)) {
switch (flags & BPF_F_HDR_FIELD_MASK) {
case 2:
csum_replace2(ptr, from, to);
break;
Expand Down Expand Up @@ -1467,10 +1468,12 @@ const struct bpf_func_proto bpf_l3_csum_replace_proto = {
static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
{
struct sk_buff *skb = (struct sk_buff *) (long) r1;
bool is_pseudo = !!BPF_IS_PSEUDO_HEADER(flags);
bool is_pseudo = flags & BPF_F_PSEUDO_HDR;
int offset = (int) r2;
__sum16 sum, *ptr;

if (unlikely(flags & ~(BPF_F_PSEUDO_HDR | BPF_F_HDR_FIELD_MASK)))
return -EINVAL;
if (unlikely((u32) offset > 0xffff))
return -EFAULT;

Expand All @@ -1482,7 +1485,7 @@ static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
if (unlikely(!ptr))
return -EFAULT;

switch (BPF_HEADER_FIELD_SIZE(flags)) {
switch (flags & BPF_F_HDR_FIELD_MASK) {
case 2:
inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
break;
Expand Down Expand Up @@ -1511,13 +1514,14 @@ const struct bpf_func_proto bpf_l4_csum_replace_proto = {
.arg5_type = ARG_ANYTHING,
};

#define BPF_IS_REDIRECT_INGRESS(flags) ((flags) & 1)

static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
{
struct sk_buff *skb = (struct sk_buff *) (long) r1, *skb2;
struct net_device *dev;

if (unlikely(flags & ~(BPF_F_INGRESS)))
return -EINVAL;

dev = dev_get_by_index_rcu(dev_net(skb->dev), ifindex);
if (unlikely(!dev))
return -EINVAL;
Expand All @@ -1526,7 +1530,7 @@ static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
if (unlikely(!skb2))
return -ENOMEM;

if (BPF_IS_REDIRECT_INGRESS(flags)) {
if (flags & BPF_F_INGRESS) {
if (skb_at_tc_ingress(skb2))
skb_postpush_rcsum(skb2, skb_mac_header(skb2),
skb2->mac_len);
Expand All @@ -1553,12 +1557,17 @@ struct redirect_info {
};

static DEFINE_PER_CPU(struct redirect_info, redirect_info);

static u64 bpf_redirect(u64 ifindex, u64 flags, u64 r3, u64 r4, u64 r5)
{
struct redirect_info *ri = this_cpu_ptr(&redirect_info);

if (unlikely(flags & ~(BPF_F_INGRESS)))
return TC_ACT_SHOT;

ri->ifindex = ifindex;
ri->flags = flags;

return TC_ACT_REDIRECT;
}

Expand All @@ -1574,7 +1583,7 @@ int skb_do_redirect(struct sk_buff *skb)
return -EINVAL;
}

if (BPF_IS_REDIRECT_INGRESS(ri->flags)) {
if (ri->flags & BPF_F_INGRESS) {
if (skb_at_tc_ingress(skb))
skb_postpush_rcsum(skb, skb_mac_header(skb),
skb->mac_len);
Expand Down

0 comments on commit 781c53b

Please sign in to comment.