[PATCH net 2/4] tls: adjust recv return with async crypto and failed copy to userspace

[Sabrina Dubroca <sd@queasysnail.net>]

process_rx_list may not copy as many bytes as we want to the userspace
buffer, for example in case we hit an EFAULT during the copy. If this
happens, we should only count the bytes that were actually copied,
which may be 0.

Subtracting async_copy_bytes is correct in both peek and !peek cases,
because decrypted == async_copy_bytes + peeked for the peek case: peek
is always !ZC, and we can go through either the sync or async path. In
the async case, we add chunk to both decrypted and
async_copy_bytes. In the sync case, we add chunk to both decrypted and
peeked. I missed that in commit 6caaf104423d ("tls: fix peeking with
sync+async decryption").

Fixes: 4d42cd6bc2ac ("tls: rx: fix return value for async crypto")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
---
I'll send a patch removing the peeked variable and simplifying the
process_rx_list call for net-next after this series lands there

 net/tls/tls_sw.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 3cdc6bc9fba6..14faf6189eb1 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -2158,6 +2158,9 @@ int tls_sw_recvmsg(struct sock *sk,
 		else
 			err = process_rx_list(ctx, msg, &control, 0,
 					      async_copy_bytes, is_peek, NULL);
+
+		/* we could have copied less than we wanted, and possibly nothing */
+		decrypted += max(err, 0) - async_copy_bytes;
 	}
 
 	copied += decrypted;
-- 
2.43.0