[PATCH net-next v4 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 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.
 - A comment in the netmem KUnit test names BUG_ON(i >= nfrags) in
   skb_segment(), which is a check that fails the segmentation now.

No functional change.

Acked-by: Mina Almasry <almasrymina@xxxxxxxxxx>
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
 net/core/filter.c   | 6 +++---
 net/core/net_test.c | 2 +-
 net/core/skbuff.c   | 5 +++--
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 09c60a58c82a..9881ac89e94c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3723,9 +3723,9 @@ 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 03203454cd19..976d14896251 100644
--- a/net/core/net_test.c
+++ b/net/core/net_test.c
@@ -1524,7 +1524,7 @@ static void netmem_ref_test_skb_segment(struct kunit 
*test)
        /* 5. Linear head_skb (nr_frags=0) + mixed pp_recycle frag_list where
         * member A has linear + frag (pp_recycle=1) and tail member B has
         * linear len == skb_headlen(A) (pp_recycle=0): keeps SG clone path
-        * synchronized without hitting BUG_ON(i >= nfrags).
+        * synchronized without failing the i >= nfrags check.
         */
        head = alloc_skb(64, GFP_KERNEL);
        list = alloc_skb(64, GFP_KERNEL);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 45cd77e153f1..29951ce11850 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5641,8 +5641,9 @@ __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