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Subject[34/35] udp/recvmsg: Clear MSG_TRUNC flag when starting over for a new packet
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

------------------


From: Xufeng Zhang <xufeng.zhang@windriver.com>

[ 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>
---
net/ipv4/udp.c | 3 +++
net/ipv6/udp.c | 3 +++
2 files changed, 6 insertions(+)

--- 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;
}

--- 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;
}




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