[PATCH net-next 05/15] net: skbuff: fail pskb_trim_rcsum() when it can't checksum the tail

[Josef Bacik <josef@xxxxxxxxxxxxxx>]

For a CHECKSUM_COMPLETE skb, pskb_trim_rcsum() subtracts the checksum
of the bytes it trims from skb->csum.  It gets that checksum from
skb_checksum(), so if the trimmed range runs into unreadable frags in a
frag_list member, or past the end of the skb, it subtracts 0 and
leaves skb->csum covering bytes that are no longer in the packet.

pskb_trim_rcsum() can already fail, and its callers drop the packet
when it does.  Use skb_checksum_full() and return its error.

Assisted-by: LLM
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
---
 net/core/skbuff.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 88ed2dd99dc0..de433d452939 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2829,9 +2829,13 @@ static int pskb_trim_rcsum_complete(struct sk_buff *skb, 
unsigned int len)
        int delta = skb->len - len;
 
        if (skb_frags_readable(skb)) {
-               skb->csum = csum_block_sub(skb->csum,
-                                          skb_checksum(skb, len, delta, 0),
-                                          len);
+               __wsum csum = 0;
+               int err;
+
+               err = skb_checksum_full(skb, len, delta, &csum);
+               if (err)
+                       return err;
+               skb->csum = csum_block_sub(skb->csum, csum, len);
                return 0;
        }
 

-- 
2.55.0