[PATCH net-next 15/15] net: update comments that still describe the skb BUG_ON()s

[Josef Bacik <josef@xxxxxxxxxxxxxx>]

The skbuff BUG_ON() conversions left a few comments behind:

 - bpf_skb_net_grow() says skb_segment() BUG()s on a frag_list with
   head_frag set at the downgraded MSS.  It fails the segmentation and
   the packet is dropped, which is still why the skb gets linearized.
 - The GSO KUnit test says the non-uniform frag_list case would hit
   BUG_ON(i >= nfrags) with SG.  That check now fails with -EINVAL.
 - The skb_to_sgvec() kernel-doc doesn't list the -EINVAL that
   __skb_to_sgvec() returns when @offset and @len run past the end of
   the skb.

No functional change.

Assisted-by: LLM
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
 net/core/filter.c   | 6 +++---
 net/core/net_test.c | 4 ++--
 net/core/skbuff.c   | 5 +++--
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 3ee1a093337e..f5bce0dc43fe 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3696,9 +3696,9 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, 
u32 len_diff,
                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.
+                * Segmenting a frag_list with head_frag true at the new MSS
+                * fails and the packet gets dropped, so linearize the skb
+                * after downgrading the MSS.
                 */
                if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO)) {
                        skb_decrease_gso_size(shinfo, len_diff);
diff --git a/net/core/net_test.c b/net/core/net_test.c
index 12a175268a01..d38dfeed163b 100644
--- a/net/core/net_test.c
+++ b/net/core/net_test.c
@@ -325,8 +325,8 @@ static void gso_test_func(struct kunit *test)
        if (tcase->id == GSO_TEST_GSO_PARTIAL)
                features |= NETIF_F_GSO_PARTIAL;
 
-       /* TODO: this should also work with SG,
-        * rather than hit BUG_ON(i >= nfrags)
+       /* TODO: this should also work with SG, rather than fail the
+        * i >= nfrags check in skb_segment()
         */
        if (tcase->id == GSO_TEST_FRAG_LIST_NON_UNIFORM)
                features &= ~NETIF_F_SG;
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b6ada54ecc57..4822f96fc1c8 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5554,8 +5554,9 @@ __skb_to_sgvec(struct sk_buff *skb, struct scatterlist 
*sg, int offset, int len,
  *
  *     Fill the specified scatter-gather list with mappings/pointers into a
  *     region of the buffer space attached to a socket buffer. Returns either
- *     the number of scatterlist items used, or -EMSGSIZE if the contents
- *     could not fit.
+ *     the number of scatterlist items used, -EMSGSIZE if the contents
+ *     could not fit, or -EINVAL if @offset and @len run past the end of
+ *     the skb.
  */
 int skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int 
len)
 {

-- 
2.55.0