udp/recvmsg: Clear MSG_TRUNC flag when starting over for a new packet

commit 9cfaa8def1c795a512bc04f2aec333b03724ca2e upstream.

Consider this scenario: When the size of the first received udp packet
is bigger than the receive buffer, MSG_TRUNC bit is set in msg->msg_flags.
However, if checksum error happens and this is a blocking socket, it will
goto try_again loop to receive the next packet.  But if the size of the
next udp packet is smaller than receive buffer, MSG_TRUNC flag should not
be set, but because MSG_TRUNC bit is not cleared in msg->msg_flags before
receive the next packet, MSG_TRUNC is still set, which is wrong.

Fix this problem by clearing MSG_TRUNC flag when starting over for a
new packet.

Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index ff6a18ea815115969c29e4f72baf852d6f0d1126..7932dc68c669097cff3a3f4d70ffdb297fd5725e 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1203,6 +1203,9 @@ csum_copy_err:
 
        if (noblock)
                return -EAGAIN;
+
+       /* starting over for a new packet */
+       msg->msg_flags &= ~MSG_TRUNC;
        goto try_again;
 }
 

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index a0a6a0849796c507551357d462f83219c0cad002..a1d3d32237dd002dd402213761f253c58193ed0c 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -443,6 +443,9 @@ csum_copy_err:
 
        if (noblock)
                return -EAGAIN;
+
+       /* starting over for a new packet */
+       msg->msg_flags &= ~MSG_TRUNC;
        goto try_again;
 }