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bpf: export helper function flags and reject invalid ones
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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>
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Daniel Borkmann authored and David S. Miller committed Jan 11, 2016
1 parent c8086f6 commit 781c53b
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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

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