This is a note to let you know that I've just added the patch titled
bpf: Fix a segment issue when downgrading gso_size
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-fix-a-segment-issue-when-downgrading-gso_size.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e734eba261f13b17ce99bf99e458504667856567
Author: Fred Li <dracodingfly@xxxxxxxxx>
Date: Fri Jul 19 10:46:53 2024 +0800
bpf: Fix a segment issue when downgrading gso_size
[ Upstream commit fa5ef655615a01533035c6139248c5b33aa27028 ]
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@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20240626065555.35460-2-dracodingfly@xxxxxxxxx [1]
Link: https://lore.kernel.org/all/668d5cf1ec330_1c18c32947@xxxxxxxxxxxxxxxxxxxxxx.notmuch [2]
Link: https://lore.kernel.org/bpf/20240719024653.77006-1-dracodingfly@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/core/filter.c b/net/core/filter.c
index 3c4dcdc7217e0..f82c27668623c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3126,13 +3126,20 @@ 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;
