2017-03-08 17:16:02

by Alexander Potapenko

Subject: [PATCH v2] net: initialize msg.msg_flags in recvfrom

KMSAN reports a use of uninitialized memory in put_cmsg() because
msg.msg_flags in recvfrom haven't been initialized properly.
The flag values don't affect the result on this path, but it's still a
good idea to initialize them explicitly.

Signed-off-by: Alexander Potapenko <[email protected]>
---
Changes since v1:
- removed KMSAN report and reproducer from the description
---
net/socket.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/socket.c b/net/socket.c
index 2c1e8677ff2d..e0757e648c0c 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1731,6 +1731,7 @@ SYSCALL_DEFINE6(recvfrom, int, fd, void __user *, ubuf, size_t, size,
/* We assume all kernel code knows the size of sockaddr_storage */
msg.msg_namelen = 0;
msg.msg_iocb = NULL;
+ msg.msg_flags = 0;
if (sock->file->f_flags & O_NONBLOCK)
flags |= MSG_DONTWAIT;
err = sock_recvmsg(sock, &msg, flags);
--
2.12.0.246.ga2ecc84866-goog

2017-03-10 01:23:18

by David Miller

Subject: Re: [PATCH v2] net: initialize msg.msg_flags in recvfrom

From: Alexander Potapenko <[email protected]>
Date: Wed, 8 Mar 2017 18:08:16 +0100

> KMSAN reports a use of uninitialized memory in put_cmsg() because
> msg.msg_flags in recvfrom haven't been initialized properly.
> The flag values don't affect the result on this path, but it's still a
> good idea to initialize them explicitly.
>
> Signed-off-by: Alexander Potapenko <[email protected]>
> ---
> Changes since v1:
> - removed KMSAN report and reproducer from the description

Applied, thank you.