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bpf: Make bpf_skb_adjust_room metadata-safe

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bpf_skb_adjust_room() may push or pull bytes from skb->data. In both cases,
skb metadata must be moved accordingly to stay accessible.

Replace existing memmove() calls, which only move payload, with a helper
that also handles metadata. Reserve enough space for metadata to fit after
skb_push.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-7-5ceb08a9b37b@cloudflare.com
This commit is contained in:
Jakub Sitnicki
2025-11-05 21:19:44 +01:00
committed by Martin KaFai Lau
parent 55ffc98b44
commit be83105d38
1 changed files with 5 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
net/core/filter.c
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@@ -3253,11 +3253,11 @@ static void bpf_skb_change_protocol(struct sk_buff *skb, u16 proto)
static int bpf_skb_generic_push(struct sk_buff *skb, u32 off, u32 len)
{
/* Caller already did skb_cow() with len as headroom,
/* Caller already did skb_cow() with meta_len+len as headroom,
* so no need to do it here.
*/
skb_push(skb, len);
memmove(skb->data, skb->data + len, off);
skb_postpush_data_move(skb, len, off);
memset(skb->data + off, 0, len);
/* No skb_postpush_rcsum(skb, skb->data + off, len)
@@ -3281,7 +3281,7 @@ static int bpf_skb_generic_pop(struct sk_buff *skb, u32 off, u32 len)
old_data = skb->data;
__skb_pull(skb, len);
skb_postpull_rcsum(skb, old_data + off, len);
memmove(skb->data, old_data, off);
skb_postpull_data_move(skb, len, off);
return 0;
}
@@ -3489,6 +3489,7 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
u8 inner_mac_len = flags >> BPF_ADJ_ROOM_ENCAP_L2_SHIFT;
bool encap = flags & BPF_F_ADJ_ROOM_ENCAP_L3_MASK;
u16 mac_len = 0, inner_net = 0, inner_trans = 0;
const u8 meta_len = skb_metadata_len(skb);
unsigned int gso_type = SKB_GSO_DODGY;
int ret;
@@ -3499,7 +3500,7 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
return -ENOTSUPP;
}
ret = skb_cow_head(skb, len_diff);
ret = skb_cow_head(skb, meta_len + len_diff);
if (unlikely(ret < 0))
return ret;