From: David Howells dhowells@redhat.com
[ Upstream commit 0d40f728e28393a8817d1fcae923dfa3409e488c ]
rxkad_verify_packet_2() has a small stack-allocated sglist of 4 elements, but if that isn't sufficient for the number of fragments in the socket buffer, we try to allocate an sglist large enough to hold all the fragments.
However, for large packets with a lot of fragments, this isn't sufficient and we need at least one additional fragment.
The problem manifests as skb_to_sgvec() returning -EMSGSIZE and this then getting returned by userspace. Most of the time, this isn't a problem as rxrpc sets a limit of 5692, big enough for 4 jumbo subpackets to be glued together; occasionally, however, the server will ignore the reported limit and give a packet that's a lot bigger - say 19852 bytes with ->nr_frags being 7. skb_to_sgvec() then tries to return a "zeroth" fragment that seems to occur before the fragments counted by ->nr_frags and we hit the end of the sglist too early.
Note that __skb_to_sgvec() also has an skb_walk_frags() loop that is recursive up to 24 deep. I'm not sure if I need to take account of that too - or if there's an easy way of counting those frags too.
Fix this by counting an extra frag and allocating a larger sglist based on that.
Fixes: d0d5c0cd1e71 ("rxrpc: Use skb_unshare() rather than skb_cow_data()") Reported-by: Marc Dionne marc.dionne@auristor.com Signed-off-by: David Howells dhowells@redhat.com cc: linux-afs@lists.infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/rxrpc/rxkad.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c index f114dc2af5cf3..5345e8eefd33c 100644 --- a/net/rxrpc/rxkad.c +++ b/net/rxrpc/rxkad.c @@ -451,7 +451,7 @@ static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb, * directly into the target buffer. */ sg = _sg; - nsg = skb_shinfo(skb)->nr_frags; + nsg = skb_shinfo(skb)->nr_frags + 1; if (nsg <= 4) { nsg = 4; } else {