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

[ Upstream commit 9cfaa8def1c795a512bc04f2aec333b03724ca2e ]

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: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 31db78ca746985165ac38118aa9ebc7e80850526..0ac88332d56a3f52ee8e216f3db9c053ff274176 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1011,6 +1011,9 @@ 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 852a07faf64a7718d0381206665f4f007843e4c6..ca520d4d9069600cb6aff363aa27f93a20a502f0 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -306,6 +306,9 @@ csum_copy_err:
 
        if (noblock)
                return -EAGAIN;
+
+       /* starting over for a new packet */
+       msg->msg_flags &= ~MSG_TRUNC;
        goto try_again;
 }