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ipv4/ip_sockglue.c: copy msg_control optval from user to kernel space

PATCH In review H Hartley Sweeten 2 participants 3 messages Jan 15, 2010 – Jan 16, 2010 1 message not in the archive

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H Hartley Sweeten

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#0 lore raw

PATCH 1/1 ipv4/ip_sockglue.c: copy msg_control optval from user to kernel space

ipv4/ip_sockglue.c: copy msg_control optval from user to kernel space

In do_ip_getsockopt the char __user *optval is used directly in IP_PKTOPTIONS for the msg.msg_control and not copied from user to kernel address space. This produces a sparse warning:

warning: incorrect type in assignment (different address spaces)
expected void *msg_control
got char [noderef] <asn:1>*optval

Fix this by using copy _from_user to set msg.msg_control.

Signed-off-by H Hartley Sweeten <[email protected]>
Cc David S. Miller <[email protected]>
Cc Alexey Kuznetsov <[email protected]>
Cc "Pekka Savola (ipv6)" <[email protected]>
Cc James Morris <[email protected]>
Cc Hideaki YOSHIFUJI <[email protected]>
Cc Patrick McHardy <[email protected]>

---

net/ipv4/ip_sockglue.c +2 -1
index cafad9b..8065456 100644
@@ -1173,7 +1173,8 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname,
 		if (sk->sk_type != SOCK_STREAM)
 			return -ENOPROTOOPT;
 
-		msg.msg_control = optval;
+		if (copy_from_user(msg.msg_control, optval, len))
+			return -EFAULT;
 		msg.msg_controllen = len;
 		msg.msg_flags = 0;
maintainer
#1 lore raw

From: H Hartley Sweeten <[email protected]>
Date: Fri, 15 Jan 2010 10:24:59 -0700

Quoted 6 lines

ipv4/ip_sockglue.c: copy msg_control optval from user to kernel space

In do_ip_getsockopt the char __user *optval is used directly in IP_PKTOPTIONS for the msg.msg_control and not copied from user to kernel address space. This produces a sparse warning:

Quoted 7 lines

warning: incorrect type in assignment (different address spaces)
expected void *msg_control
got char [noderef] <asn:1>*optval

Fix this by using copy _from_user to set msg.msg_control.

Signed-off-by H Hartley Sweeten <[email protected]>

This isn't right.

We want the 'optval' pointer itself, not the data it points to, stored in msg.msg_control

And 'msg_control' is, in this case a user pointer.

It just isn't annotated (along with the rest of struct msghdr) with "__user" because we mix the usage of this object with kernel and user pointers.

How did you test your change?

A message that is not in the archive (sent off-list or not yet received): [email protected]

maintainer
#3 lore raw

From: "H Hartley Sweeten" <[email protected]>
Date: Sat, 16 Jan 2010 01:22:21 -0500

Quoted 6 lines · David Miller
Quoted 1 line

How did you test your change?

Hmm... I saw the sparse warning and tried this to fix it. The code compiled fine and the warning was gone. When I booted the resulting kernel I didn't see any issues. I must not have went down this code path in my testing.

I'm going to ask you a second time.

What was your test case? How did you test the change?

I don't think you tested your change at all besides seeing that gcc would accept the code and sparse stopped spitting out a warning. And you're vagueness about your testing methodology will only work to confirm my suspicions.

I find it unlikely, at best, for you to have tested that code path, as 'msg' is an uninitilized stack variable at this point in the code, so 'msg->msg_control' is going to be a garbage pointer, and therefore copying to it would result in a crash.

I don't even think you read and understood the code you are editing.

I suspect you just wanted to kill the sparse warning somehow, you found a way that made the compiler and sparse eat it, and you simply ran with it.

And that really upsets me.

Fixing sparse warnings should not be a mindless exercise. You should understand the code you are changing.