Commit fa5ef655615a for kernel
commit fa5ef655615a01533035c6139248c5b33aa27028
Author: Fred Li <dracodingfly@gmail.com>
Date: Fri Jul 19 10:46:53 2024 +0800
bpf: Fix a segment issue when downgrading gso_size
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: 2be7e212d5419 ("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
diff --git a/net/core/filter.c b/net/core/filter.c
index 4cf1d34f7617..f3c72cf86099 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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;