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bpf: Fix a segment issue when downgrading gso_size

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Linearize the skb when downgrading gso_size because it may trigger a
BUG_ON() later when the skb is segmented as described in [1,2].

Fixes: 2be7e212d5 ("bpf: add bpf_skb_adjust_room helper")
Signed-off-by: Fred Li <dracodingfly@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/all/20240626065555.35460-2-dracodingfly@gmail.com [1]
Link: https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@willemb.c.googlers.com.notmuch [2]
Link: https://lore.kernel.org/bpf/20240719024653.77006-1-dracodingfly@gmail.com
This commit is contained in:
Fred Li 2024-07-19 10:46:53 +08:00 committed by Daniel Borkmann
parent 13c9b702e6
commit fa5ef65561
1 changed files with 11 additions and 4 deletions
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15
net/core/filter.c
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@ -3548,13 +3548,20 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
if (skb_is_gso(skb)) {
struct skb_shared_info *shinfo = skb_shinfo(skb);
/* Due to header grow, MSS needs to be downgraded. */
if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO))
skb_decrease_gso_size(shinfo, len_diff);
/* Header must be checked, and gso_segs recomputed. */
shinfo->gso_type |= gso_type;
shinfo->gso_segs = 0;
/* Due to header growth, MSS needs to be downgraded.
* There is a BUG_ON() when segmenting the frag_list with
* head_frag true, so linearize the skb after downgrading
* the MSS.
*/
if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO)) {
skb_decrease_gso_size(shinfo, len_diff);
if (shinfo->frag_list)
return skb_linearize(skb);
}
}
return 0;