[net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

Subsystems: networking [general], networking [tcp], the rest

7 messages, 6 authors, 2021-02-25 · open the first message on its own page

[net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: Arjun Roy <hidden>
Date: 2021-02-11 21:22:53 

From: Arjun Roy <redacted>

Explicitly define reserved field and require it and any subsequent
fields to be zero-valued for now. Additionally, limit the valid CMSG
flags that tcp_zerocopy_receive accepts.

Fixes: 7eeba1706eba ("tcp: Add receive timestamp support for receive zerocopy.")
Signed-off-by: Arjun Roy <redacted>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <redacted>
Suggested-by: David Ahern <redacted>
Suggested-by: Leon Romanovsky <leon@kernel.org>
Suggested-by: Jakub Kicinski <kuba@kernel.org>
---
 include/uapi/linux/tcp.h |  2 +-
 net/ipv4/tcp.c           | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 42fc5a640df4..8fc09e8638b3 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -357,6 +357,6 @@ struct tcp_zerocopy_receive {
 	__u64 msg_control; /* ancillary data */
 	__u64 msg_controllen;
 	__u32 msg_flags;
-	/* __u32 hole;  Next we must add >1 u32 otherwise length checks fail. */
+	__u32 reserved; /* set to 0 for now */
 };
 #endif /* _UAPI_LINUX_TCP_H */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e1a17c6b473c..9896ca10bb34 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2030,6 +2030,7 @@ static int tcp_zerocopy_vm_insert_batch(struct vm_area_struct *vma,
 		err);
 }
 
+#define TCP_VALID_ZC_MSG_FLAGS   (TCP_CMSG_TS)
 static void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
 			       struct scm_timestamping_internal *tss);
 static void tcp_zc_finalize_rx_tstamp(struct sock *sk,
@@ -4152,13 +4153,21 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
 			return -EFAULT;
 		if (len < offsetofend(struct tcp_zerocopy_receive, length))
 			return -EINVAL;
-		if (len > sizeof(zc)) {
+		if (unlikely(len > sizeof(zc))) {
+			err = check_zeroed_user(optval + sizeof(zc),
+						len - sizeof(zc));
+			if (err < 1)
+				return err == 0 ? -EINVAL : err;
 			len = sizeof(zc);
 			if (put_user(len, optlen))
 				return -EFAULT;
 		}
 		if (copy_from_user(&zc, optval, len))
 			return -EFAULT;
+		if (zc.reserved)
+			return -EINVAL;
+		if (zc.msg_flags &  ~(TCP_VALID_ZC_MSG_FLAGS))
+			return -EINVAL;
 		lock_sock(sk);
 		err = tcp_zerocopy_receive(sk, &zc, &tss);
 		release_sock(sk);
-- 
2.30.0.478.g8a0d178c01-goog

Re: [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: Jakub Kicinski <kuba@kernel.org>
Date: 2021-02-12 02:09:36 

On Thu, 11 Feb 2021 13:21:07 -0800 Arjun Roy wrote:
+		if (unlikely(len > sizeof(zc))) {
+			err = check_zeroed_user(optval + sizeof(zc),
+						len - sizeof(zc));
+			if (err < 1)
+				return err == 0 ? -EINVAL : err;
nit: return err ? : -EINVAL;

 			len = sizeof(zc);
 			if (put_user(len, optlen))
 				return -EFAULT;
 		}
 		if (copy_from_user(&zc, optval, len))
 			return -EFAULT;
+		if (zc.reserved)
+			return -EINVAL;
+		if (zc.msg_flags &  ~(TCP_VALID_ZC_MSG_FLAGS))
nit: parens unnecessary

But neither is a big deal:

Acked-by: Jakub Kicinski <kuba@kernel.org>

Re: [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: patchwork-bot+netdevbpf@kernel.org
Date: 2021-02-12 03:11:09 

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Thu, 11 Feb 2021 13:21:07 -0800 you wrote:
From: Arjun Roy <redacted>

Explicitly define reserved field and require it and any subsequent
fields to be zero-valued for now. Additionally, limit the valid CMSG
flags that tcp_zerocopy_receive accepts.

Fixes: 7eeba1706eba ("tcp: Add receive timestamp support for receive zerocopy.")
Signed-off-by: Arjun Roy <redacted>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <redacted>
Suggested-by: David Ahern <redacted>
Suggested-by: Leon Romanovsky <leon@kernel.org>
Suggested-by: Jakub Kicinski <kuba@kernel.org>

[...]
Here is the summary with links:
  - [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.
    https://git.kernel.org/netdev/net-next/c/3c5a2fd042d0

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: Dan Carpenter <hidden>
Date: 2021-02-15 12:05:08 

Hi Arjun,

url:    https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520
config: x86_64-randconfig-m001-20210209 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>
Reported-by: Dan Carpenter <redacted>

smatch warnings:
net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len'

vim +/len +4158 net/ipv4/tcp.c

3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3896  static int do_tcp_getsockopt(struct sock *sk, int level,
3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3897  		int optname, char __user *optval, int __user *optlen)
^1da177e4c3f41 Linus Torvalds           2005-04-16  3898  {
295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09  3899  	struct inet_connection_sock *icsk = inet_csk(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3900  	struct tcp_sock *tp = tcp_sk(sk);
6fa251663069e0 Nikolay Borisov          2016-02-03  3901  	struct net *net = sock_net(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3902  	int val, len;

"len" is int.

[ snip ]
05255b823a6173 Eric Dumazet             2018-04-27  4146  #ifdef CONFIG_MMU
05255b823a6173 Eric Dumazet             2018-04-27  4147  	case TCP_ZEROCOPY_RECEIVE: {
7eeba1706eba6d Arjun Roy                2021-01-20  4148  		struct scm_timestamping_internal tss;
e0fecb289ad3fd Arjun Roy                2020-12-10  4149  		struct tcp_zerocopy_receive zc = {};
05255b823a6173 Eric Dumazet             2018-04-27  4150  		int err;
05255b823a6173 Eric Dumazet             2018-04-27  4151  
05255b823a6173 Eric Dumazet             2018-04-27  4152  		if (get_user(len, optlen))
05255b823a6173 Eric Dumazet             2018-04-27  4153  			return -EFAULT;
c8856c05145490 Arjun Roy                2020-02-14  4154  		if (len < offsetofend(struct tcp_zerocopy_receive, length))
05255b823a6173 Eric Dumazet             2018-04-27  4155  			return -EINVAL;


The problem is that negative values of "len" are type promoted to high
positive values.  So the fix is to write this as:

	if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length))
		return -EINVAL;

110912bdf28392 Arjun Roy                2021-02-11  4156  		if (unlikely(len > sizeof(zc))) {
110912bdf28392 Arjun Roy                2021-02-11  4157  			err = check_zeroed_user(optval + sizeof(zc),
110912bdf28392 Arjun Roy                2021-02-11 @4158  						len - sizeof(zc));
                                                                                                        ^^^^^^^^^^^^^^^^
Potentially "len - a negative value".


110912bdf28392 Arjun Roy                2021-02-11  4159  			if (err < 1)
110912bdf28392 Arjun Roy                2021-02-11  4160  				return err == 0 ? -EINVAL : err;
c8856c05145490 Arjun Roy                2020-02-14  4161  			len = sizeof(zc);
0b7f41f68710cc Arjun Roy                2020-02-25  4162  			if (put_user(len, optlen))
0b7f41f68710cc Arjun Roy                2020-02-25  4163  				return -EFAULT;
0b7f41f68710cc Arjun Roy                2020-02-25  4164  		}

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: David Ahern <hidden>
Date: 2021-02-15 15:06:52 

On 2/15/21 5:03 AM, Dan Carpenter wrote:
Hi Arjun,

url:    https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git e4b62cf7559f2ef9a022de235e5a09a8d7ded520
config: x86_64-randconfig-m001-20210209 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>
Reported-by: Dan Carpenter <redacted>

smatch warnings:
net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len'

vim +/len +4158 net/ipv4/tcp.c

3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3896  static int do_tcp_getsockopt(struct sock *sk, int level,
3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3897  		int optname, char __user *optval, int __user *optlen)
^1da177e4c3f41 Linus Torvalds           2005-04-16  3898  {
295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09  3899  	struct inet_connection_sock *icsk = inet_csk(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3900  	struct tcp_sock *tp = tcp_sk(sk);
6fa251663069e0 Nikolay Borisov          2016-02-03  3901  	struct net *net = sock_net(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3902  	int val, len;

"len" is int.

[ snip ]
05255b823a6173 Eric Dumazet             2018-04-27  4146  #ifdef CONFIG_MMU
05255b823a6173 Eric Dumazet             2018-04-27  4147  	case TCP_ZEROCOPY_RECEIVE: {
7eeba1706eba6d Arjun Roy                2021-01-20  4148  		struct scm_timestamping_internal tss;
e0fecb289ad3fd Arjun Roy                2020-12-10  4149  		struct tcp_zerocopy_receive zc = {};
05255b823a6173 Eric Dumazet             2018-04-27  4150  		int err;
05255b823a6173 Eric Dumazet             2018-04-27  4151  
05255b823a6173 Eric Dumazet             2018-04-27  4152  		if (get_user(len, optlen))
05255b823a6173 Eric Dumazet             2018-04-27  4153  			return -EFAULT;
c8856c05145490 Arjun Roy                2020-02-14  4154  		if (len < offsetofend(struct tcp_zerocopy_receive, length))
05255b823a6173 Eric Dumazet             2018-04-27  4155  			return -EINVAL;


The problem is that negative values of "len" are type promoted to high
positive values.  So the fix is to write this as:

	if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length))
		return -EINVAL;

110912bdf28392 Arjun Roy                2021-02-11  4156  		if (unlikely(len > sizeof(zc))) {
110912bdf28392 Arjun Roy                2021-02-11  4157  			err = check_zeroed_user(optval + sizeof(zc),
110912bdf28392 Arjun Roy                2021-02-11 @4158  						len - sizeof(zc));
                                                                                                        ^^^^^^^^^^^^^^^^
Potentially "len - a negative value".

get_user(len, optlen) is called multiple times in that function. len < 0
was checked after the first one at the top.

Also, maybe I am missing something here, but offsetofend can not return
a negative value, so this checks catches len < 0 as well:

	if (len < offsetofend(struct tcp_zerocopy_receive, length))
		return -EINVAL;

Re: [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: Dan Carpenter <hidden>
Date: 2021-02-15 16:08:54 

On Mon, Feb 15, 2021 at 08:04:11AM -0700, David Ahern wrote:
On 2/15/21 5:03 AM, Dan Carpenter wrote:
quoted
Hi Arjun,

url:    https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537 
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git  e4b62cf7559f2ef9a022de235e5a09a8d7ded520
config: x86_64-randconfig-m001-20210209 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>
Reported-by: Dan Carpenter <redacted>

smatch warnings:
net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len'

vim +/len +4158 net/ipv4/tcp.c

3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3896  static int do_tcp_getsockopt(struct sock *sk, int level,
3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3897  		int optname, char __user *optval, int __user *optlen)
^1da177e4c3f41 Linus Torvalds           2005-04-16  3898  {
295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09  3899  	struct inet_connection_sock *icsk = inet_csk(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3900  	struct tcp_sock *tp = tcp_sk(sk);
6fa251663069e0 Nikolay Borisov          2016-02-03  3901  	struct net *net = sock_net(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3902  	int val, len;

"len" is int.

[ snip ]
05255b823a6173 Eric Dumazet             2018-04-27  4146  #ifdef CONFIG_MMU
05255b823a6173 Eric Dumazet             2018-04-27  4147  	case TCP_ZEROCOPY_RECEIVE: {
7eeba1706eba6d Arjun Roy                2021-01-20  4148  		struct scm_timestamping_internal tss;
e0fecb289ad3fd Arjun Roy                2020-12-10  4149  		struct tcp_zerocopy_receive zc = {};
05255b823a6173 Eric Dumazet             2018-04-27  4150  		int err;
05255b823a6173 Eric Dumazet             2018-04-27  4151  
05255b823a6173 Eric Dumazet             2018-04-27  4152  		if (get_user(len, optlen))
05255b823a6173 Eric Dumazet             2018-04-27  4153  			return -EFAULT;
c8856c05145490 Arjun Roy                2020-02-14  4154  		if (len < offsetofend(struct tcp_zerocopy_receive, length))
05255b823a6173 Eric Dumazet             2018-04-27  4155  			return -EINVAL;


The problem is that negative values of "len" are type promoted to high
positive values.  So the fix is to write this as:

	if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length))
		return -EINVAL;

110912bdf28392 Arjun Roy                2021-02-11  4156  		if (unlikely(len > sizeof(zc))) {
110912bdf28392 Arjun Roy                2021-02-11  4157  			err = check_zeroed_user(optval + sizeof(zc),
110912bdf28392 Arjun Roy                2021-02-11 @4158  						len - sizeof(zc));
                                                                                                        ^^^^^^^^^^^^^^^^
Potentially "len - a negative value".

get_user(len, optlen) is called multiple times in that function. len < 0
was checked after the first one at the top.
What you're describing is a "Double Fetch" bug, where the attack is we
get some data from the user, and we verify it, then we get it from the
user a second time and trust it.  The problem is that the user modifies
it between the first and second get_user() call so it ends up being a
security vulnerability.

But I'm glad you pointed out the first get_user() because it has an
ancient, harmless pre git bug in it.

net/ipv4/tcp.c
  3888  static int do_tcp_getsockopt(struct sock *sk, int level,
  3889                  int optname, char __user *optval, int __user *optlen)
  3890  {
  3891          struct inet_connection_sock *icsk = inet_csk(sk);
  3892          struct tcp_sock *tp = tcp_sk(sk);
  3893          struct net *net = sock_net(sk);
  3894          int val, len;
  3895  
  3896          if (get_user(len, optlen))
  3897                  return -EFAULT;
  3898  
  3899          len = min_t(unsigned int, len, sizeof(int));
  3900  
  3901          if (len < 0)
                    ^^^^^^^
This is impossible.  "len" has to be in the 0-4 range because of the
min_t() assignment.  It's harmless though and the condition should just
be removed.

  3902                  return -EINVAL;
  3903  
  3904          switch (optname) {
  3905          case TCP_MAXSEG:

Anyway, I will create a new Smatch warning for this situation.

Also, maybe I am missing something here, but offsetofend can not return
a negative value, so this checks catches len < 0 as well:

	if (len < offsetofend(struct tcp_zerocopy_receive, length))
		return -EINVAL;
offsetofend is (unsigned long)12.  If we compare a negative integer with
(unsigned long)12 then negative number is type promoted to a high
positive value.

	if (-1 < (usigned long)12)
		printf("dan is wrong\n");

regards,
dan carpenter

Re: [net-next] tcp: Sanitize CMSG flags and reserved args in tcp_zerocopy_receive.

From: Arjun Roy <hidden>
Date: 2021-02-25 23:01:30 

On Mon, Feb 15, 2021 at 8:02 AM Dan Carpenter [off-list ref] wrote:
On Mon, Feb 15, 2021 at 08:04:11AM -0700, David Ahern wrote:
quoted
On 2/15/21 5:03 AM, Dan Carpenter wrote:
quoted
Hi Arjun,

url:    https://github.com/0day-ci/linux/commits/Arjun-Roy/tcp-Sanitize-CMSG-flags-and-reserved-args-in-tcp_zerocopy_receive/20210212-052537
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git  e4b62cf7559f2ef9a022de235e5a09a8d7ded520
config: x86_64-randconfig-m001-20210209 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>
Reported-by: Dan Carpenter <redacted>

smatch warnings:
net/ipv4/tcp.c:4158 do_tcp_getsockopt() warn: check for integer overflow 'len'

vim +/len +4158 net/ipv4/tcp.c

3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3896  static int do_tcp_getsockopt(struct sock *sk, int level,
3fdadf7d27e3fb Dmitry Mishin            2006-03-20  3897            int optname, char __user *optval, int __user *optlen)
^1da177e4c3f41 Linus Torvalds           2005-04-16  3898  {
295f7324ff8d9e Arnaldo Carvalho de Melo 2005-08-09  3899    struct inet_connection_sock *icsk = inet_csk(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3900    struct tcp_sock *tp = tcp_sk(sk);
6fa251663069e0 Nikolay Borisov          2016-02-03  3901    struct net *net = sock_net(sk);
^1da177e4c3f41 Linus Torvalds           2005-04-16  3902    int val, len;

"len" is int.

[ snip ]
05255b823a6173 Eric Dumazet             2018-04-27  4146  #ifdef CONFIG_MMU
05255b823a6173 Eric Dumazet             2018-04-27  4147    case TCP_ZEROCOPY_RECEIVE: {
7eeba1706eba6d Arjun Roy                2021-01-20  4148            struct scm_timestamping_internal tss;
e0fecb289ad3fd Arjun Roy                2020-12-10  4149            struct tcp_zerocopy_receive zc = {};
05255b823a6173 Eric Dumazet             2018-04-27  4150            int err;
05255b823a6173 Eric Dumazet             2018-04-27  4151
05255b823a6173 Eric Dumazet             2018-04-27  4152            if (get_user(len, optlen))
05255b823a6173 Eric Dumazet             2018-04-27  4153                    return -EFAULT;
c8856c05145490 Arjun Roy                2020-02-14  4154            if (len < offsetofend(struct tcp_zerocopy_receive, length))
05255b823a6173 Eric Dumazet             2018-04-27  4155                    return -EINVAL;


The problem is that negative values of "len" are type promoted to high
positive values.  So the fix is to write this as:

    if (len < 0 || len < offsetofend(struct tcp_zerocopy_receive, length))
            return -EINVAL;

110912bdf28392 Arjun Roy                2021-02-11  4156            if (unlikely(len > sizeof(zc))) {
110912bdf28392 Arjun Roy                2021-02-11  4157                    err = check_zeroed_user(optval + sizeof(zc),
110912bdf28392 Arjun Roy                2021-02-11 @4158                                            len - sizeof(zc));
                                                                                                        ^^^^^^^^^^^^^^^^
Potentially "len - a negative value".

get_user(len, optlen) is called multiple times in that function. len < 0
was checked after the first one at the top.
What you're describing is a "Double Fetch" bug, where the attack is we
get some data from the user, and we verify it, then we get it from the
user a second time and trust it.  The problem is that the user modifies
it between the first and second get_user() call so it ends up being a
security vulnerability.

But I'm glad you pointed out the first get_user() because it has an
ancient, harmless pre git bug in it.

net/ipv4/tcp.c
  3888  static int do_tcp_getsockopt(struct sock *sk, int level,
  3889                  int optname, char __user *optval, int __user *optlen)
  3890  {
  3891          struct inet_connection_sock *icsk = inet_csk(sk);
  3892          struct tcp_sock *tp = tcp_sk(sk);
  3893          struct net *net = sock_net(sk);
  3894          int val, len;
  3895
  3896          if (get_user(len, optlen))
  3897                  return -EFAULT;
  3898
  3899          len = min_t(unsigned int, len, sizeof(int));
  3900
  3901          if (len < 0)
                    ^^^^^^^
This is impossible.  "len" has to be in the 0-4 range because of the
min_t() assignment.  It's harmless though and the condition should just
be removed.

  3902                  return -EINVAL;
  3903
  3904          switch (optname) {
  3905          case TCP_MAXSEG:

Anyway, I will create a new Smatch warning for this situation.
quoted
Also, maybe I am missing something here, but offsetofend can not return
a negative value, so this checks catches len < 0 as well:

      if (len < offsetofend(struct tcp_zerocopy_receive, length))
              return -EINVAL;
offsetofend is (unsigned long)12.  If we compare a negative integer with
(unsigned long)12 then negative number is type promoted to a high
positive value.

        if (-1 < (usigned long)12)
                printf("dan is wrong\n");

regards,
dan carpenter

Thank you for the catch. I will send out a fix momentarily.

Actually, now I'm curious - why does do_tcp_getsockopt get called so
many times, per getsockopt target - rather than just using the
originally read value?

-Arjun
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