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bpf: try harder on clones when writing into skb 

When we're dealing with clones and the area is not writeable, try
harder and get a copy via pskb_expand_head(). Replace also other
occurences in tc actions with the new skb_try_make_writable().

Reported-by: Ashhad Sheikh <ashhadsheikh394@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2016-02-19 23:05:25 +01:00 committed by David S. Miller
parent 21cafc1dc2
commit 3697649ff2
4 changed files with 24 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/linux/skbuff.h
View File

@ -2630,6 +2630,13 @@ static inline int skb_clone_writable(const struct sk_buff *skb, unsigned int len
skb_headroom(skb) + len <= skb->hdr_len;
}
static inline int skb_try_make_writable(struct sk_buff *skb,
unsigned int write_len)
{
return skb_cloned(skb) && !skb_clone_writable(skb, write_len) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
}
static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
int cloned)
{

19
net/core/filter.c
View File

@ -1364,9 +1364,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
*/
if (unlikely((u32) offset > 0xffff || len > sizeof(sp->buff)))
return -EFAULT;
if (unlikely(skb_cloned(skb) &&
!skb_clone_writable(skb, offset + len)))
if (unlikely(skb_try_make_writable(skb, offset + len)))
return -EFAULT;
ptr = skb_header_pointer(skb, offset, len, sp->buff);
@ -1439,9 +1437,7 @@ static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
return -EINVAL;
if (unlikely((u32) offset > 0xffff))
return -EFAULT;
if (unlikely(skb_cloned(skb) &&
!skb_clone_writable(skb, offset + sizeof(sum))))
if (unlikely(skb_try_make_writable(skb, offset + sizeof(sum))))
return -EFAULT;
ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
@ -1488,9 +1484,7 @@ static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags)
return -EINVAL;
if (unlikely((u32) offset > 0xffff))
return -EFAULT;
if (unlikely(skb_cloned(skb) &&
!skb_clone_writable(skb, offset + sizeof(sum))))
if (unlikely(skb_try_make_writable(skb, offset + sizeof(sum))))
return -EFAULT;
ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
@ -1734,6 +1728,13 @@ bool bpf_helper_changes_skb_data(void *func)
return true;
if (func == bpf_skb_vlan_pop)
return true;
if (func == bpf_skb_store_bytes)
return true;
if (func == bpf_l3_csum_replace)
return true;
if (func == bpf_l4_csum_replace)
return true;
return false;
}

8
net/sched/act_csum.c
View File

@ -105,9 +105,7 @@ static void *tcf_csum_skb_nextlayer(struct sk_buff *skb,
int hl = ihl + jhl;
if (!pskb_may_pull(skb, ipl + ntkoff) || (ipl < hl) ||
(skb_cloned(skb) &&
!skb_clone_writable(skb, hl + ntkoff) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
skb_try_make_writable(skb, hl + ntkoff))
return NULL;
else
return (void *)(skb_network_header(skb) + ihl);
@ -365,9 +363,7 @@ static int tcf_csum_ipv4(struct sk_buff *skb, u32 update_flags)
}
if (update_flags & TCA_CSUM_UPDATE_FLAG_IPV4HDR) {
if (skb_cloned(skb) &&
!skb_clone_writable(skb, sizeof(*iph) + ntkoff) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
if (skb_try_make_writable(skb, sizeof(*iph) + ntkoff))
goto fail;
ip_send_check(ip_hdr(skb));

18
net/sched/act_nat.c
View File

@ -126,9 +126,7 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
addr = iph->daddr;
if (!((old_addr ^ addr) & mask)) {
if (skb_cloned(skb) &&
!skb_clone_writable(skb, sizeof(*iph) + noff) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
if (skb_try_make_writable(skb, sizeof(*iph) + noff))
goto drop;
new_addr &= mask;
@ -156,9 +154,7 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
struct tcphdr *tcph;
if (!pskb_may_pull(skb, ihl + sizeof(*tcph) + noff) ||
(skb_cloned(skb) &&
!skb_clone_writable(skb, ihl + sizeof(*tcph) + noff) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
skb_try_make_writable(skb, ihl + sizeof(*tcph) + noff))
goto drop;
tcph = (void *)(skb_network_header(skb) + ihl);
@ -171,9 +167,7 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
struct udphdr *udph;
if (!pskb_may_pull(skb, ihl + sizeof(*udph) + noff) ||
(skb_cloned(skb) &&
!skb_clone_writable(skb, ihl + sizeof(*udph) + noff) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC)))
skb_try_make_writable(skb, ihl + sizeof(*udph) + noff))
goto drop;
udph = (void *)(skb_network_header(skb) + ihl);
@ -213,10 +207,8 @@ static int tcf_nat(struct sk_buff *skb, const struct tc_action *a,
if ((old_addr ^ addr) & mask)
break;
if (skb_cloned(skb) &&
!skb_clone_writable(skb, ihl + sizeof(*icmph) +
sizeof(*iph) + noff) &&
pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
if (skb_try_make_writable(skb, ihl + sizeof(*icmph) +
sizeof(*iph) + noff))
goto drop;
icmph = (void *)(skb_network_header(skb) + ihl);